@ Wolf Kanno: FF XIII and FF Versus XIII, and even Agito XIII DO NOT share the same world, and it has already been confirmed. They only share the same mythology of Crystals, but they do not share the exact same story, gameplay, characters, or even atmosphere.
Also, Nomura isn't going to be the director of XIII, he's the director of Versus XIII. Toriyama is the director for XIII. Also, I agree with Duality, these three XIII titles are probably going to be so different from each other that they could easily be called XIII, IV, and XV.
Anyhow, the differences are already obvious. XIII's Crystals has the power to create, and they're like Gods, only different... Lightning was even chosen to destroy the world by one of the 'Crystals'. Meanwhile Versus XIII's Crystals are simply objects that hold power, much like the traditional FF Crystals... and only one Crystal is left in the world of Versus XIII... so yeah, it is so different.. I'm not so sure about Agito though.
So I disagree that Square is getting ahead of themselves because these 3 games appear to be going in very different directions.