^
"Q. Are you going to be involved in the soundtrack for Kingdom Hearts III?
Utada: I don?t think so, I don?t know. Probably not.
Mr. Utada: We said no to Disney. Ohh?

Q. You turned down Disney?
Mr. Utada: Yeah. Because they don?t pay."

I hope they work something out, I remember someone mentioning recently that Nomura confirmed she would be back, but it wasn't stated if for KH: Birth by Sleep or KH III.

One thing for sure, it will NOT be the same if she is not the one singing the theme songs.