Man, this post is gigantic. I went kinda nuts writing this, pardon the word vomit. There's probably something I forgot to expand on fully because I was jumping around so much, pardon weird cliffhangers I'll elaborate on them if needed.
Anyway, I want to look at Pokemon I think won't be in SV's dex but probably will be in SV.
Looking at SWSH 1.0's Inaccessible Pokemon to Parse Trends for SV's Pokemon Inclusions
I was thinking about the initial crop of ~430 Pokemon we got when Sword and Shield first came out. Specifically, I wanted to pay attention to the Pokemon outside the Galar Dex, Pokemon you either couldn't interact with or were very likely not to interact with before Pokemon Home's launch. That's a pretty interesting crop of Pokemon! They're Pokemon so important, they felt the need to put them in the game even if most of the casual playerbase won't ever interact with them! That's a pretty good indication there are some reasons why these Pokemon are getting extra attention, and those philosophies might very well carry over to SV. Let's take a look at that and see if there are any trends we can gauge!
Sword and Shield went out of their way to add these Pokemon to the roster despite being completely inaccessible without transfers:
>>Pokemon Outside the Galar Dex in SWSH 1.0<<
Bulbasaur Family
Squirtle Family
Mewtwo
Mew*
Celebi
Jirachi
The Swords of Justice Trio
Reshiram
Zekrom
Kyurem
Keldeo
The Alolan Starter Families
Cosmog Family
Necrozma
Marshadow
Zeraora
Meltan Family
*Mew is still accessible in base SWSH without Home through the Pokeball Controller but more on that later
There are a few trends in here I think stand out. In particular, I think most of these inclusions revolve around one central premise:
Welcome Returning Players Back, Keep Them Invested, Make Hardcore fans.
Not alienating people from game to game is a challenge. Doing that while also finally cutting the dex size is a challenge. If you are on Smogon reading this, you are a very entrenched player who'll probably feel a bit of disappointment with a smaller Pokemon roster, but will still be pretty deeply attached to the franchise.
What about someone fairly newer to the franchise? What if they picked up Sun and Moon or LGPE and want to play the new game? Having some of the most precious Pokemon they've spent the most time with in older adventures feels important in keeping them invested. I felt some major whiplash when most of my favorites from Gen 1 and 2 weren't in Gen 3. I spend more time playing Silver than Sapphire in 2003, and my interest in the series didn't really recover until Bayleef and the Johto pokemon I loved came back in Coliseum. Cushioning that blow is hard, but an excellent way to soften it is keeping your dearest partners, or what's likely to be most players' dearest partners, around for the next ride.
Obviously, what Pokemon we bond to is a bit scattershot and can depend on so many factors and individual experiences. That said, there are a few predictable features on the road with standout playthrough-defining Pokemon. Let's look at these inclusions and distill these into a few principles to use to make a list of likely returning Pokemon!
1) Keep your first buddy: Starters! I think most every kid holds their starter dear. In the older games, it's your level 70 beatstick while you drag around a weird ensemble of under leveled pokemon. In 2019, I had kids at our pokemon league that felt bad taking their starters off of their pvp teams for casual battles. Kids get pretty close with their cool little dude and being able to use it, or NOT being able to use it, feels like a deciding factor in keeping some folks on board. I feel this is pretty solid grounds for explaining why the Alola starters are back at DLC 0.
Bulbasaur and Squirtle are a little rockier. While they're starters from the most recent pokemon game at the time of SWSH, they're not actually, you know, the starters in the most recent Pokemon game. I'll go into them just a bit later.
2) Keep your reward for a playthrough well done: Continuing on with that theme of making players who played the last game feel like there's solid carryover even in the face of roster cuts, keeping the cover legendaries in is a great move. You played through Sun or Moon and got your big legendary. You played through USUM and got your Necrozma. You trekked through Cerulean cave and caught a Mewtwo. Now you get to keep it and use it even more in the next game!
3) Keep your special mythical rewards: Mythical Pokemon are money. Owning one's not required for dex purposes and it's almost always because they've got a slight pay-to-win taintedness to them. Making your customer feel like they wasted money on a movie ticket or a controller or a game release is big feel bad, so preserving that is important. Showing them that enjoying a Pokemon experience rewards them with a cool gamepiece for years to come can have some serious positive impact.
Quick anecdote: I for one never bought LGPE. I probably would have never played it if it weren't for Meltan making me charge through it. If I didn't borrow the game from a friend, or if I were a whiny kid asking their parents, I probably might have bought LGPE at some point for the sake of Pokedex completion. Pokemon like this have draw. Including them is important. Hell, I know some folks who bought that stupid pokeball controller twice to get another mew in SWSH! If this is a trend they see in multiple consumers, these particular Pokemon are important inclusions!
A big chunk of these mythical Pokemon fit this bill. Mew got shilled by reggie at E3 a year prior and keeping that accessory alive for SWSH is a payday. Marshadow and Zerora put butts in seats in japan. Celebi is a much loser fit into the mold, especially given that Lugia and Ho-oh aren't in to be encapsulated in the "playthrough well done" part. That said, given it was the driving selling point behind the crystal vc release, I'm willing to include it here. Jirachi is... well, it's a bit of a loose fit for later.
The only notable emission from the list of Gen 7 mythicals here is Magearna, who existed as a pre-release hype pokemon akin to Manaphy or Zoroark. Honestly though, the fact Magearna is a permanent fixture of SM and USUM and isn't attached to any early adapter whatever or some incentive to buy a game without any other new Pokemon (Meltan) I feel is good enough reason not to bring it over initially.
Note that Jirachi and Keldeo don't fit under here at all. More on them later.
The above three I believe are really solid patterns you can grok from the DLC 0 inclusions in SWSH. The next two are on what I think are less stable grounds.
4) Completing cycles seems important: Remember the week-ish before the datamine where we saw the whole Pokdex and saw Charmander but no Bulbasaur and Squirtle? There was blood in the streets! Completing cycles is a pretty satisfying for a player to see in a game, and a pretty frustrating thing to see not put in a game. People love symmetry, it's like a major part of game design. A cycle of Pokemon like a starter trio or a legendary trio being left unfulfilled is a frustrating affair, especially when it's as shoved in the player's face as Charizard in SWSH.
With that said...
The Hisuian starters are a giant glowing neon sign that they don't feel bound to cycle completion. Sure, they make their own cycle, but you do have to admit it feels a bit weird to 2/3rds of a starter trio left out in the cold. It feels a little less weird because PLA is a smaller scope game than a normal Pokemon adventure, but I can still see them going either way on including the remaining six Pokemon families in SV. Because of this, I'll be breaking my thoughs of what's probably in SV in two with this force having power and no power.
5) Just do some extra stuff too I guess? - Okay, some of this I just can't distill into something tangible well. Jirachi and the Gen 5 legendaries being in the game is pretty weird. I don't know why they're there, and I can't think of any ongoing events that would tie them to being a priority to being in the game. All I can do is speculate as to maybe there being some scrapped ideas or ease of implementation that let them slip in. Maybe the whole "Wishing Piece" thing made them want to tie it into Jirachi? It seems plausible given the SWSH bonus in BDSP is a Jirachi. Maybe that crowned tundra footprint thing for the musketeers was planned for the base game? Maybe doing the legwork for the solarizers' inclusion made implementing kyruem easy? Hell, maybe even like, the way the solarizers were programmed in Gen 7 you need Kyurem things in the game too not to break it lol? Pokemon is on a massive pile of tech debt so I wouldn't be surprised one little fiddling upends a bunch of stuff after Spinda got shafted in BDSP. Or hell, maybe they were just nostalgic for gen 5 or something.
It's way too open here and all I can do is baselessly speculate! The takeaway here though is murky. I don't think anything can be planned around this well at all. I just might expect some weird inclusions like "huh why are the legendary dogs in this game?" once SV is released.
What can we take away from all this? Well, if we assume these principles are things Gamefreak wants to stick to to keep players on board, we can infer what I think is a pretty reasonable list of things we'll see in SV. Using these principles, I am pretty confident that SV will allow us to import the pokemon from previous games, even if they're no in the Pokedex:
>>Pokemon Likely To Be In SV Base on SWSH Inaccessible Pokemon Trends<<
More Moderate Reading: (Principles 1-3 Apply, No 4)
The Galar Starter Trio Familiies
The Sinnoh Starter Trio Families
The Hisuian Starter Trio Families
Zacian
Zamazenta
Calyrex + Steeds
Dialga
Palkia
Arceus
Zarude
Manaphy (and 
)
Darkrai
Shaymin
More Generous Reading (Principles 1-4 Apply)
All Pokemon in prior list
The remaining Johto, Unova, and Alola Starter Families
Eternatus
Urshifu
Giratina
Mew
Jirachi
Let's elaborate a bit:
Keep Your Starters - Gen 8 had a big heap of starters to deal with, what a mess! It gets even worse with cycle completion, but we'll get to that later. Still, given what they did with SWSH, I feel confident all our first partner pals from the newer switch games will be tagging along for SV adventures.
Keep Your Reward - With three games, there are a lot of rewards to go through. Zacian, Zamazenta, Dialga, and Palkia are all totally analogous to keeping Solgaleo, Lunala, and Mewtwo as rewards from the Gen 7 games. Calyrex I feel is also on this same level as a big bad restricted legendary and your reward for completing SWSH and the DLC. Arceus, despite being a mythic, also fits this bill given he was central to the latest installment.
Keep Your Mythics - We have a big crop of Mythics to run with for Gen 8. Zarude's our one lone new Mythic who gets to stick around an extra gen for selling tickets. Manaphy, Shaymin, and Darkrai were all featured prominently as promotional Pokemon and fit the same bill Meltan and Mew did in the previous generation.
Altogether, this makes for 22 Pokemon, which is well under the 33 SWSH added as mostly inaccessible prior to Home, leaving plenty of wiggle room for extra surprise inclusions like SWSH's Gen 5 legendary stuff.
There are a few glaring omissions here I think are also very likely to get in, but a bit too reliant on cycle completion or some other factor to pin it to the more certain list.
Giratina - This is like the most borderline Pokemon for nearly getting on the rock solid list, but I've got just a tiny bit of doubt thanks to Necrozma. Part of me feels that Necrozma is operating less as completing a trio and more just on acting as a "keeping your reward" sort of thing for USUM. Still, I think having Giratina on is close to a near lock, just not as close as Dialga and Palkia.
Eternatus - I guess Zacian, Zamazeta, and Eternatus are a trio of sorts, but boy, they feel the most disconnected out of any trio of cover legend - cover legend - extra legend we've had of the lot. Eternatus is also on the wings of that cycle completion going for Giratina, but it feels far more likely to be excluded with how disconnected it is from the cover legendaries. If only Pokemon Gun had released with it on the cover...
Urshifu - I had Urshifu on the first list initially, but I talked myself out of it. I feel as if rewarding / incentivizing purchase of the SWSH expansion is going to be a driving force behind these likely post dex inclusions in SV, but Urshifu don't have to do a ton for that. Adding Naganadel for example, a Pokemon that explicitly requires USUM and would be a nice reward for purchasing that game in SWSH, wasn't included in the base SWSH roster. I think we'll get a little nod towards the DLC purchase, but I think Calyrex being the big bad imposing legendary is more likely. Still, Urshifu was on the cover for the DLC and the DLC box set, so I can see it cropping up easy. On that note, I feel the weight of Urshifu and Calyrex are way, way higher than the other featured Pokemon in the expansions, so I feel they're the only ones in contentions for being nearly certain postdex locks.
Mew and Jirachi - Mew and Jirachi were featured as mythical rewards for having save data on your console. I feel they're also extremely likely, especially given the popularity of Mew, but feel they're just a tad less steady than the Gen 4 mythics who do the same thing and also rewarded early purchases.
The remaining starters - This one is... weird. Part of my feels like PLA shows they're okay with sectioning a little group like this out. Part of me feels the Venusaur-Blastoise thing in SWSH makes them very likely, especially given PLA was just a far smaller game. Adding six whole extra pokemon families seems like a fair bit of extra work, especially given so much of this is going six years without things like Serperior available, but the extra symmetry feels like it matters enough to spur them into including the lot.
That's just about it! For the record though, I don't want this to come off as like a trend that gamefreak *has* to follow. Sometimes I think online discussion gets a bit mired in trends that might like fit the mold of what a dev has done, but not something they're held to for future developments (the discourse about things that were already spirits in SSBU not being fighter contenders rubbed me poorly). I'm in agreeance with a lot of AquaticPanic's stance on patterns. I want this to be less "what if this is a pattern to be paid off in this new game!?" and more "These indicate some tangible forces that boost player satisfaction and drive sales probably are being thought about and are still likely on the table."
Finally, to be clear, I also think a lot more Pokemon are almost assuredly in the game too, but this post is ungodly long enough. I think basically every new Pokemon and form in PLA is a shoe-in to be in SV. I'm also almost certain eternal fan favorites like Eevee, Mewtwo, and the Kanto starters won't miss the game. Those discussions are for another day! This however I feel is way more solid grounds for discussion and analysis and I felt was worth posting in its current state. I'm just operating off of that tiny bit of content that was mostly inaccessible at the start of SWSH's lifespan to see if we can extrapolate anything. Excited to see how others view these sorts of trends.
also I willed charizard x and cosmog and galar slowbro's typing into existance so im VERY right and should not be questioned on my speculation abilities nyeh 
