Kingdom Hearts is the only game Id buy a new console for(Yes Im a fanboy, shut up), heck its the only reason Sony's gaming department has gotten my money, minus the Vita, that thing is too convincing, KH would just be the icing on the cake for that
As for what you said, Roxas didnt spend the whole summer there, he spent 7 days, his mind was wiped in a way to make him THINK it was the whole summer. Plus the real kids never even met roxas to be friends with him.
DD will have Augmented Reality features for the 3ds, so thats cool.
EDIT2:Agreed LuigiHann, no more retelling Disney stories, but the second half was of them exploring the worlds and having honest plot related issues to the story(such as Riku being found in Mulans world).