Now that I have time to put down my thoughts:
Having megas present in the filler title could also imply they could be back in gen 8? Else why would you put them in a title meant to introduce people to Pokemon games?
That's what I'm wondering. If so, I'm also wondering if maybe they could even add new Mega Evos. Not too far-fetched now that we know there's going to be at least one new Pokemon (that special gift Pokemon), Alolan Forms (though I doubt we'll see any new Alolan forms, though what would be a neat twist if they had Kanto versions of Alolan Pokemon), and now Mega Evolutions returning. All Pokemon not in the original Gen I games. Though before going on, let's take a quick moment to look at the Gen I Pokemon that have Mega Evolutions (and their Types):
Venusaur (Grass/Poison),
Charizard (Fire/Flying & Fire/Dragon),
Blastoise (Water),
Beedrill (Bug/Poison),
Pidgeot (Normal/Flying),
Alakazam (Psychic),
Slowbro (Water/Psychic),
Gengar (Ghost/Poison),
Kangaskhan (Normal),
Pinsir (Bug/Flying),
Gyarados (Water/Dark),
Aerodactyl (Rock/Flying), &
Mewtwo (Psychic & Psychic/Fighting)
We're missing a Ground-, Steel-, Electric-, Ice-, and Fairy-type.
Now here's the final stage Gen I Pokemon who don't have a Mega Evolution (whose final stage wasn't introduce in another gen, sorry Magnezone): Butterfree, Raticate, Fearow, Arbok, Raichu, Sandslash, Nidoqueen, Nidoking, Clefable, Ninetales, Wigglytuff, Vileplume, Parasect, Venomoth, Dugtrio, Persian, Golduck, Primeape, Arcanine, Poliwrath, Machamp, Victreebel, Tentacruel, Golem, Rapidash, Farfetch'd, Dodrio, Dewgong, Muk, Cloyster, Hypno, Kingler, Electrode, Exeggutor, Marowak, Hitmonlee, Hitmonchan, Weezing, Seaking, Starmie, Mr. Mime, Jynx, Tauros, Lapras, Ditto, Vaporeon, Jolteon, Flareon, Omastar, Kabutops, Snorlax, Articuno, Zapdos, Moltres, Dragonite, & Mew.
First, if they were to introduce new Mega Evolutions, priority will go to filling the missing Type gaps:
Ground: Sandslash*, Nidoqueen, Nidoking, Dugtrio*, Golem*, Marowak*
Electric: Raichu*, Electrode, Jolteon, Zapdos
Ice: Dewgong, Cloyster, Jynx, Lapras, Articuno
Fairy: Clefable, Wigglytuff, Mr. Mime
As you noticed, we're missing one Type because, due to them seemingly not wanting future gen Pokemon in the game (yet is allowing a completely new Pokemon, Alolan forms, and Mega Evos...) we have a problem. Actually, as you can tell by the asterisks, we have a few complications:
Steel-type: There's no "Kanto" candidate for Steel-type. Now, one solution is maybe having a Pokemon gain the Steel-type upon Mega Evolving, though which one? Looking at the list I'm not seeing that many likely candidates. There's Cloyster though I think it would like to keep its Ice-typing for a Mega Evo that'll have Skill Link so it can get STAB Icicle Spear. Electrode could be another choice, knocking down two missing Types with one Mega Evolution by having an Electric/Steel-type. Only other one I see is maybe Snorlax, make it bulkier and heavier for a strong STAB Heavy Slam and referencing it's immunity to poisons in its dex entry (yes, it has Immunity for that, though if its part Steel-type it can get another Ability). Of course there's another problem with Snorlax getting a Mega and that it has a Signature Z-Move and GF seemed to have been careful not to give a Pokemon with a Mega Evo a signature Z-Move... and Alolan Form. And that's where both solution #2 and complication #2 combine:
Alolan Forms: As you can tell from the Ground-types, some of the candidates for Mega Evolution have an Alolan Form. So here's a question: if they give a Pokemon with an Alolan Form a Mega Evo what happens? Would both become the same Mega Evo even if it doesn't match one of them? Would the Mega be a combination of the two (not likely in my opinion due to how open the concept of regional variants is)? Or would they make two separate forms of Mega Evo? I think the latter would be the easiest and one open for more possibilities. Because if they do that then we not only get candidates for Steel-type (Sandslash & Dugtrio) but also for Electric (Golem), Ice (Sandslash, Ninetales), and Fairy (Ninetales). Heck, with just Sandslash alone that'll cover three of the missing Types. But if they don't want to do that, and they decide to just make Cloyster/Electrode/Snorlax/whoever into a part Steel-type, even though there's potential candidates for Electric, Ice, and Fairy for Ground that just leaves Nidoqueen and Nidoking and it doesn't seem fair to give one a Mega Evo over the other (though I guess they could give another Pokemon part Ground-type; Arbok? Dodrio?).
Speaking of fairness, that's another issue to consider. Beedrill/Pidgeot/Alakazam gets a Mega but Butterfree/Fearow/Machamp don't? It's kind of unfair that Jynx has been left behind by Electabuzz and Magmar in the evo department, shouldn't it get some limelight (though it'll then fall back behind if those two's evos ever get Megas). Seems odd Mewtwo, a clone, gets Mega but the original, Mew, doesn't (though it has a signature Z-Move putting it on the same boat as Snorlax). And poor normal Raichu, can we just throw it a bone or something (even if it also means Alolan Raichu gets a Mega, maybe make Kantonian Raichu an Electric/Fighting or Electric/Steel or something to help it stand out more)? And that's not factoring in popular Pokemon (Arcanine & Dragonite come to mind) and Pokemon who could really benefit from a Mega (too many to list so I'll just joke a say Farfetch'd :P).
So much to consider... IF they're going to make more Megas for LGPE. If not, maybe because of all this complication, then this is a mute point though if they ever want to make new Mega the question concerning Regional Variants would still be there (and whether they want to give Mega to Pokemon who also go Signature Z-Moves).
I just hope that you don't have to catch a Diglett to fight Surge.
But yeah, actually adding the Megas is nice at least, considering we haven't seen any of them in any major form for at least 4 years (unless you count Giovanni's Mega Mewtwo from USUM). Though considering the handholding of these games, something like Zard's megas would just break the game even more.
There's also Geodude and Sandshrew. Diglett also isn't too hard to get.
And yeah, don't think difficulty balance is really that much of an issue with GF here. *Sigh* But hey, maybe they can give Gym Leaders/Elite Four some Mega? Hmm, thinking about it, at the very least the Champion should have a Mega though that brings up the question who will be the Champion? If Trace it would have to be another Pokemon other than his Starter, though Red and Blue they could do something interesting with.
Oh, and I like how Surge is dubbed the "Lightning Tough Guy".
Possible title change? Originally he was called "The Lightning American"... except there's no America in the Pokemon World. We have Unova that's New York (and parts of New Jersey) and Alola that's Hawaii. In B2W2 they jokes about that by having someone in the Pokemon World Tournament question is Surge is from Unova. So it makes sense that they may have decided to change his title to get rid of real world reference. That said, wouldn't "Lightning Soldier" make for a better title than "Lightning Tough Guy"?
There's going to be some food for thought until we see them in action - more likely in a Pokémon Direct.
Well since we just got a Smash Direct (Simon, Richter, Chrom, Dark Samus, & King K Rool HYPE!), wouldn't be surprised if it's now Pokemon's turn for a Direct (and in addition to LGPE news give us some actual info about the Gen 8 games...).
I wonder if Z-Moves will return.
If Megas are back I wouldn't be surprised. Another way to over prepare kids for their Gym Leader battle: hide the Z-Crystal of a Type with an advantage nearby... which would probably explain why they want to make sure you have a Pokemon that's super effective.
Not to mention to also get Pikachu's and Eevee's Signature Z-Move (I wonder if they'll change the animation for Eevee's where it's only Vaporeon, Jolteon, and Flareon; or they hide the other five in silhouette). Though what would they do concerning the Pikashunium Z?
Actually, I suppose it would be fair to wonder that, just like I asked with Mega Evos, would they make new exclusive Z-Crystals? Plenty of Gen I Pokemon to do something unique with. Normal Raichu (if they don't give it a Mega at least toss it its own Z-Move), Meowth, Machamp, Farfetch'd, Electrode, Hitmonlee, Hitmonchan, Mr. Mime, Jynx, Tauros, Ditto, Winged Mirages, etc..
I think there's a decent chance that the E3 demo was just a really early build without hold items implemented, or its a menu option you unlock later in the game. While you can argue that removing items would be in line with the norms this game is breaking, I think it's equally possible that items are tutoralized in some way. I can totally see the game locking a gym away from you until you force a Pokemon to hold an item for example!
I would like this to be the case. E3 Demo just wanted to focus on the core gameplay, no reason to take out Hold Items and Abilities yet also include all these other things that weren't in the original games. The ONLY reason they wouldn't have Held Items or Abilities is because they wanted to make the transfer between LGPE and GO more simpler... but having Megas now completely throw that idea out the window. If there is no Held Items, only way I can see around this is that during battle you go into Items and use the Mega Stone on the Pokemon like you would a Potion/Ether/X Battle item. Though if they do that it's less likely they'll have Z-Moves unless you do the same thing and it'll ask which move you want to turn into the Z-Move and then execute the Z-Move.
But if that's the case this would also mean Abilities not being in which would REALLY effect the Mega Evos, some relying on their Abilities to give them an extra oomph whether in power or tactics.
BTW, does this hint Megas for GO?