I only read the first post, and potentially someone mentioned this lol.
Nomura said in an interview, that the Secret Ending is a image of the end. So you can realize that.
Actually I was thinking about this relation to the Deep Dive vid. The deep dive trailer didnt offer very much informations about the KH II. The Birth by Sleep trailer is little different, its more dramatic etc. But in fact, it was only a very little part of the game itself. Really like the Deep Dive vid.