Yeah, Z, those are all good questions and I think a few of them will be answered, but not all of them. We'll learn everything in due time with the future KH games.
Well, at least we know how Terra, Master Xehanort, Xemnas, Ansem, and Ansem Seeker of Darkness are all related thanks to BBS, and I bet we'll see a return of Xion, Axel, and maybe (hopefully) Roxas. Even if it's just an image or something, they will apear again, because they're all tied in together through Sora. They can't be simply forgotten.