Personally I doubt it or at the very least it won't be extensive, considering Gogoat's name, the fact that its the only thing that's showcased in the promotional artwork of the feature* and there is no confirmation that we will be using it elsewhere. And we had this sort of thing happened before, Amity Square allowed only a limited amount Pokémon, most already having overworld sprites in the game. *And it has Pokésaddles. That would be hard to implement on some Pokémon. I really hope I'm wrong though.