Update: Looks like the u3music Twitter account is stepping back from the previous statement:
I apologize for what I said. I was little confused when asked whether we would be involved in Kingdom Hearts III. As of now it's undecided.— u3music (@u3music) October 18, 2013
Kingdom Hearts III wouldn't feel right without a theme song by Japanese pop star Hikaru Utada, would it? Thankfully we now have confirmation of what was otherwise simply expected, since the singer's father, Teruzane Utada, gave a simple affirmative reply to a fan on Twitter.
Hikaru Utada's previous themes for Kingdom Hearts and Kingdom Hearts II were "Simple and Clean" and "Sanctuary," respectively.