Why? If he gets both meowstic and aegislash, I find enough. However, mega lucario will probably count as a Kalos mon, eventually.
Unless they are genuinely going to give him more Pokemon in Journeys than even in Unova, I still think 1 from any generation is fine with Kanto and Galar being the only exceptions.
Generation 1- Dragonite, Gengar, technically Farfetch'd (though it will evolve into an 8th generation Pokemon)
Generation 2- Tyranitar/Espeon
Generation 3- Flygon
Generation 4- Lucario (Riolu)
Generation 5- Chandelure.......maybe Zoroark if not Chandelure than maybe Volcorona for the bug typing.
Generation 6- Aegislash is the only one that stands out to me, since I can't get the one I want from this generation (unless I get a Sinnohan Regional variant which is sure as hell ain't going to happen) but oh well.
Generation 7- Golisopod is the only that really stands out here, though honestly I would just prefer Nagandel just permanently stay with his Alola team or he uses Incineroar.
Generation 8- Since I've given up on what I really want except two choices: Sirfetch'd (not my choice), Grimmsnarl/Frosmoth (my choice), Toxtricity (would be a nice addition), Dragapault (not my choice but fan favorite), and Corviknight (back up giant Pokemon, will be pointless though since Ash would have Dragonite and Flygon and I honestly doubt he would get a third passenger riding Pokemon though that might not figure at all. ***I also excluded Rillaboom because I honestly don't care about the starters any more ***
At this point not counting pre-evolutions that's approximately (1 per generation that he hasn't gotten anything yet and excluding Galar): That's going to be roughly 12 captures that we already looking at that's definitely MORE than Unova already.
So no I don't expect any generation to really get more than 1 except Kanto (for obvious reasons) and Galar (newest generation).
Kalos - Don't know and I honestly don't care since Phantump can't happen -_-
DP remakes, let's hope for a regional variant. Any typing mixed with Ghost for it would work fine with me, especially if it means that it won't have a trade evolution potentially, who knows maybe Trevenant could evolve into an actual next stage Pokemon?
If Goh ends up getting a Pikachu then Ash can get a Trevenant. But if we are talking wish lists again then I want his Kalos mon to be a Tyrantrum as I have been patiently waiting for him to own and command in battle with a fossil Pokémon, so I am hoping that this is the series that I get my wish.
While yes technically in can happen, I'm not too confident in believing that Go getting Pikachu matters at all.
All it does is open the possibility that they are willing to share species where Pikachu was more than likely anyway due to Go's goal. It's unlikely that Go's Pikachu will be seen that much anyway. Since he has Raboot/Sobble to care for.