The Kingdom Hearts 3D Ultimania guide book is out today, and it has the expected interview with series mastermind Tetsuya Nomura.
A brief summary at FF Reunion reveals that the interview contains a teaser for the next entry (or entries) in the KH series. Nomura says that they've started making a variety of movements for the new title(s) in the series. He believes they'll be able to make an announcement pretty soon.
The interview also contains some of those obnoxious "censored" comments, where little bits are blocked out. If you can read Japanese, here's what FF Reunion wrote:
Nomura also said that there are no plans at present for Birth By Sleep 2 or a "Final Mix" version of KH3D. Square Enix previously released updated "Final Mix" versions of Birth By Sleep and Kingdom Hearts II.