Ok, finally got to watch the direct and the Treehouse stuff and now I am much less optimistic about more old Pokémon being implemented at later points.
I mean, I won't say I can't understand. Obviously with so many Pokémon, and every time even more being add, having every game be ready to have every single Pokémon ever (along with every form and variation they can get) would make transitioning to new consoles or models or whatever a pain in the ass. I get it. Still, it is really sad.
I know having every monster in the game is probably something Pokémon exclusive. Not a single Digimon game I played had every Digimon released yet (even when they weren't that many), I remember the same with Monster Rancher or any other. But those are not Pokémon. Each series do their own things and one of the best things about Pokémon was having all of them in the game, in the same place, very noticeably part of the same thing.
I loved the fact Bank was not readily available when XY and S&M came out, forcing people to use whatever Kalos/Alola gave you. I loved that Unova didn't gave you anything old and without resorting to trade from old gens you would need to use new, and only new, pokémon. Just like having tournaments accept only regional dex pokémon, those strategies are good to make people get out of their comfort zone and give a chance to the new features - and I particularly have my own rule of only using newly implemented pokémon when I play a new gen (Caterpie-line excused). But still, at some point, every Pokémon game would allow you to have all of them there, at some point you are allowed to have all your favorites, from whatever generation, without distinction or prejudice, in a single team. That was a big part of the Pokémon charm, it was not something from the past.
It is also worrisome when they announce future games will also follow this new pattern. This means we'll inevitably have some unlucky pokémon that will be gone for many years from the main games.
I was looking specifically after SwSh with its possibility of having multiple saves so I could finally use all of the old 'mon I never got a chance to use because I never felt like deleting my original playthroughs (not to mention to have one ideal playthrough with my Dream Team, finally complete now that Grookey was introduced and took the 6th spot). That was on me, it is not a flaw of the game to not answer a very specific and individual demand, but still now the thought of "should I skip this game and wait for the third improved version?" has seriously crossed my mind for the first time ever. I am sure I will not do that because I can't resist the hype, but still… for the first time ever. And that can't be a good sign.