I hope they pump more new Pokémon in the upcoming game, the new ones are nice and all, but I want a bigger scale.
I hope they make a new Champion which actually pops out somewhere during your journey such as Cynthia did. Honestly, Diantha is a disappointment she just seems like a random movie star that happened to have snagged up some powerful Pokémons and talks as if she read a old document of bonds of Trainer and it's Pokémon. No offensive.
I hope they also introduce a trio-legendary aside from the main ones. Maybe even a duo, sure they don't need to go extreme as in B/W2, but more events with legendaries would be cool too. Maybe a side-story line involving some legendaries in the post-game? /hopes
"The third game usual have more post-game content" Good. Because I'm waiting for seasons, pokemon world tournament something as Pokémon contest, something as Hollow Tree/Black City and difficulty options. You know? Actually something to keep you entertained and something worth doing. They could even bring swarms back like in B/W2 where each day you can encounter Pokémon you usual don't during your journey. I don't know what a fairly good or a perfect thing would be in the post-game. I could see them doing a Mega-Evolution Tower, where you test your skill with the Mega evolution and you get a new Mega stone each 50 floors or something, that's something that Gamefreak would do in my point of view.