Its been announced already, the songs theme song "Passion" will be done by the famed "Utada Hikaru" for her touching work making "Simple and Clean" fr the Original game.
I can never be 100% until it is actually released, but I find it highly doubtful they will make it a Japanese version of the song on the English game, only because of the english dubbing they did for it in the first game. They might do a remix, you never know. I think they will proabably do it for KH2 as well. Im just not as sure about that as I am with the english dubbing though.