It would be the funniest move ever if SE simply announced that Versus XIII won't be finished because it's turned out to be too much work. "We had things under control until Nomura started talking about airships, world maps and ... towns. What does he think this is, the PS1 era?"
But, really, they're going to have to release something there just to save face. There's no way the thing is coming out before 2013 at the earliest anyway, and 7 years from announcement to release would already be enough of an embarassment.
As for me, I'm going to vote for KHIII as most likely to come out first.
It's obvious Nomura's more interested in this series. In the time since Versus XIII's development was announced (May 2006, if I remember correctly), three completely new titles in the KH series have been developed and released (coded, 358/2 Days, Birth by Sleep); two remakes have been released, one of which is a remake of one of the already new titles (Re:Chain of Memories, Re:coded); two Final Mix editions have been released (KHII FM+, Birth by Sleep FM); and one completely new title is in development (Dream Drop Distance).
Nomura doesn't really give a shit about Versus XIII.