OK, this whole "dream sequence" thing is NOT going to happen, so get over yourselves! SE is much deeper than ruining an awesome series by ending it with the whole damn thing being just a dream. Come on, how stupid can you be people be? Firstly, the whole "dream sequence" thing has been done too many times, and frankly it's done by people who don't know how to end thing so they just say it was all a dream. Secondly, a lot of people would be pissed off, and Nomura knows that. You think he's dumb, or something, and would pull the "it was all a dream" bull s**t? I don't think so.
The reason for Sora asking if this was all a dream, or not, was simply because it all felt so surreal. Think about it: if you were experiencing the same thing too wouldn't you think it was a dream at first? What happened in KH isn't normal, everyday things so of course someone might mistake the events for a dream until they realized what they were thinking, experiencing was indeed real.
Sheesh!