Kingdom Hearts Dream Drop Distance will be out in Japan on March 29th 2012. So, after that date spoilers will probably start appearing so be careful.
Also, there will be a bundle which will come with a Kingdom Hearts branded 3DS:
The bundle will also contain an AR Card containing a Dream Eater that is harder to obtain in the game without the AR Card. No pricing for the bundle yet and only the game itself has been confirmed for North America & Europe as of this writing.
Finally in honor of the 10 years of Kingdom Hearts, there will be a "10th anniversary box". What is included in this box is currently unknown.