Think Kingdom Hearts. Keep it simple. I believe it would play similar to the other Kingdom Hearts titles, except for the fact that it would be next gen. I do believe Nomura has 2 Kingdom Heart's projects he has to work on. One involves being on the handheld, the other is most likely on the next gen console.
Although I believe Final Fantasy Vs. 13 has some elements that would influence gameplay. Nomura did say a while back that this year was big for Kingdom Hearts and there will be some new interesting projects.
But I would not call it Kingdom Hearts 3. Its a new series involving Kingdom Hearts.