That day has not been announced as of yet, since Nomura seems more focused on the release of 358/2 Days. It will most likely be for the PlayStation 3 however.
Kingdom Hearts 3 has not been released anywhere and the release date of it at present is unknown. It will most likely be for PS3. However 358/2 Days is coming out in Fall of this year to the USA and...
Although no one knows for sure, Tetsuya Nomura (Creator of previous Kindom Hearts and the Final Fantasy's) Has revealed that in 2009 Final Fantasy XIII and XIII Versus shall come out, not revealing...