What do you think is next for Pokemon?

I wouldn't. There is literally no way to make a pokemon game last an area ~5 times the size of what we have already played and have it feel fresh the entire way through. They would either need to increase the level cap (lol not happening), make everything and everywhere more compact, so that you rush through every area with less leveling (would suck). Not to mention the obvious, 40 gym leaders and possibly multiple elite fours would get old incredibly fast.
And I would be much more interested in exploring a brand new area than revisiting a place I've already been through extensively.
Could they bring an area back as postgame content again? Sure? As a main game in its own right? I hope not.
I think they hit the nail right on the head with Black/White 2s world tournament, letting you battle old Gym leaders and other important trainers. (Though they should have included the main character from Black/White 1 somewhere too, but that is a seperate discussion).

Or they can go with the Anime version and have your Pikachu deleveled to like level 10 when you reenter a new area xD Though I admit that would be pretty sad and annoying lol.