I dont know if this has been said, but when you look at it Sora's neclace piece seems to fit the key part of the Kingdom KEy perfectly, well if it was bigger, maybe the kingdom key needed to be completed, and Sora is the missing piece?
OK here it goes, just speculation, but as i remember the knight u fight against in KH2FM said he "chose Xenahort". In the movie he takes the Kingdom Key, so could it be Xenahort was to have the key, but lost it. Also, if he could pick maybe the others did as well because the female knight seemed to be the only one to come out of all that unscaved, because the youngest was frozen and the leaders mind look like it got taken over by the old man. So back to what i was saying, the female knight was the only one to use magic, and she had the kyblade of the dark realm which is Mickeys and he is trained alot in magic by Yen Sid, which i assume is why he was holding the Star Seeker Keyblade, because he probaly got it from Yen Sid recently to fight, which leaves the youngest who picked up the keyblade of the twilight realm, Rikus Way to the Dawn, either left it, or did indeed pick Riku somehow.
OK ive been thinking about this recently since ive started replaying KH2. You all know the part after you defeat Demyx, and a rock knocks Goofy out and the king donald and sora run off, and right after Goofy is all happy and cool. To me i dont think thats Goofy, i feel Goofy got captured and thats someone else, im just guessing. How do you guys feel?