I'm enticed by the aspect of 3D depth... If any title could get something powerful out of that, it'd be KH... Dive into the deep of darkness 8D! No, but KH just has a lot of depth-related themes.
And what's this about sudden character switching? From what that quote says, the changes will be more or less random. There's probably a bit more to this than just that. Especially since a lot of story things would require specific characters. Not that they couldn't make cutscenes where the character is the one it needs to be for that particular scene. Dunno, we'll see.
An interesting idea would be if it's not just Sora and Riku that switch out like this. The trailer makes that a possibility imo. Think about it, one moment you are fighting with Sora against Xemnas, all of a sudden you change to Riku and Xemnas changes into Ansem, the fight carries on etc.