In a recent interview with Gemanga magazine, Tetsuya Nomura sat down to talk about his current project, FFVSXIII. However, he made several references to KH3. Although it is not currently confirmed if the game will ever be made, his statements hint at it quite blatently.

"Concerning the Kingdom Hearts series, Tetsuya Nomura cannot work on Final Fantasy Versus XIII and Kingdom Hearts III at the same time, because it requires far too much work. He prefers to concentrate on Final Fantasy Versus XIII first, then develop Kingdom Hearts III. He would like Final Fantasy Versus XIII to be the last game he directs in regards to the Final Fantasy series, because the pressure is too overwhelming. Also, the next Kingdom Hearts game may be revealed early this fall."

Source: Jeux-France.com