Oh! Utada said she never played any of Kingdom Hearts games, because she's not good with RPG-like kind of games (such Final Fantasy, and so on), that's the reason why you could easily tell she doesn't mention that game that much! Since she's not really interested in this game, one may wonder, indeed, if she is going to make the new theme song for the game, and sincerely, I hope so!! Do you realize I have known her first because of "Simple and Clean" (which is a situation many of her fan actually know)! One thing I'm sure of: it would definitely wouldn't be the same, a Kingdom Hearts game without Utada's sweet voice? I'm not sure I would get used to it, and I may even be less closer from Kingdom Hearts! What I mean is, despite the fact I deeply love that game, every time I think about it, I automatically think of Utada Hikaru! Which is normal, since I played every Kingdom Hearts that ever released until this present days (impatient for the 3rd) and each theme song of is game was made by Utada!
I'm not sure I'd be into hearing another voice, edged to my favorite game!