Don't you see. Square is not going to release this in the U.S. because of one thing: the PS3. That's right.
I remember reading that the PS3 is going to be able to play imported games including PS2 imports. By not releasing Final Mix and CoM in the U.S, it's going to give gamers especially KH fans more of an incentive to buy the PS3 just so they can play Final Mix without having to take apart a game system. This is all a big corporate plan by Square who has good ties with Sony to get U.S. gamers to buy the PS3. By getting them to buy the PS3, not also are their import sales going to increase, but they would now have plenty of PS3 owners who will be able to buy their new PS3 games.
So there you have it. Final Mix and CoM is just the bait. The bait to get people to buy the PS3. Very clever plan if you ask me.