I hope the formula of towns, gyms, rivals, evil teams and routes is shaken up a bit. The battling is still fun, but the progression of the game is too predictable now - I want to be surprised by a new area or new gym puzzle!
And I hope the new music is made as well as the previous four gens; they ruined the HG/SS music by making it the worst possible compromise of orchestral and 8-bit like. D/P was a great example of where the balance was right - not too orchestral as to be ambient and bland with no melody.