I agree about everything, last gen, I was one of the few who put rain manually through Prankster Tornadus + Damp Rock, and the fact that he Hurricane with it, amazing. I do not agree about it being only manually, or only automatic, a combination of both, will be most likely on every team (Maybe not realized immediately but players will resort to it soon)Weather will be on a timer, so I think you'll need multiple weather setters. I think Rain hyper offensive is gonna have Politoed together with Tornadus setting weather manually with Kingdra as the main rain abuser. I think weather will look more like the manual weather rain offensive that we sometimes saw last gen in UU, than the Politoed weather wars that we saw in OU. ALSO keep in mind Politoed won't have leftovers so it'll be a bit easier to wear down. If it DOES have leftovers, the Kingdra/Ludicolo/Kabutops/whoever sweeps will be cut a lot shorter
It'll be similar to last gen OU in the sense that we'll see weather and we'll see dragon spam, but weather is gonna work differently. Depending on how things play out, it might even be easier. If weather isn't dominant, it could be really easy to keep your own weather up. I played a bit of rain this gen, and it was easy to keep rain up on my side of the field if the opponent wasn't using a sun starter (Char Y is somewhat common, but most matches I was able to keep rain up).
I don't know about some of what Professional2341 said is going to be falling into UU, but I'm sure that UU's walls will be able to handle what's thrown at them, especially when it looks like Vaporeon and Dragalge and maybe even Trevenant are going to join.
And weather being on a timer definitely affects weather sweepers. I've fought a few weather teams, and while they are powerful, the fact that there's only 6 turns to sweep prevents weather from being overpowered. Weatherless offense has a huge bonus in that there isn't a timer on their sweep.
Furthermore, I don't think rain would necessarily would be the superior weather. Most of the fire types in UU have either Huge offensive stats (Darmanitan, Chamdelure), or a great move/movepool (Victini, Arcanine). Sun is able to use grass types, and even had its own mega, Mega-Houndoom. I don't think Ninetales will be banned because of several factors, namely bulky waters, the fact that rain setters have their own STAB boosted by the weather, and Stealth Rock. Many fire types are also frail.
And Jolteon, unlike Raikou, lacks Calm Mind and Aura Sphere and therefore a way to get past Snorlax, and is outclassed defensively by Zapdos.
The pokemons that I mentioned, are UU Statistics, Salamence is the one that has the least chance of falling to UU, but as a Dragon Dancer, he is outclassed by Dragonite and CharX, and the only good niche is Scarf Moxie, I also forgot to mention Metagross, another powerhouse, will be falling into UU for sure. Even Umbreon can't take CB Meteor mash so lightly
252+ Atk Choice Band Metagross Meteor Mash vs. 252 HP / 0 Def Umbreon: 229-271 (58.1 - 68.7%) -- guaranteed 2HKO after Leftovers recovery
CB Bullet Punch will also wreck.
And i never said Rain is superior, it never was, people just used it more, in fact, Sun will be more superior this gen thnx to CharY and the many super-good fire types in UU, Lilligant is very good there too. And if Venosaur (not mega) falls too, GG.
I don't see how Jolteon is outclassed by any electric-type other than Arceus-Electric, Zekrom, Rotom-W, ad maybe Rotom-H, other than that? No, not Manectric, his mega, or Raiku. Jolteon is fast, has the ability to carry Specs and STILL not be outsped. Volt Switch Specs is really good, part of the main reason Jolteon was OU, and Raiku was UU, and with weather falling, if you want to run Thunder, Jolteon with Specs would do crazy damage, Raikou cannot carry Specs (Scarf is superior on him), or has to use Calm Mind. Phazing, Clear Smog (Gastrodon and Amoonguss), and finally, Haze are there, very common, and will easily cut your plan in setting up, Bulky Intimidate Phazing Arcanine is a thing you know.