Posted on the official forums by Aradune (aka Brad McQuaid):

Guess we should've guessed it, seeing as how M$ is funding them, but you'd think of all people, Brad would have at least ensured seperate serversTrue, we're totally focussed on the PC game right now and nothing's confirmed either way as to whether we'll have an Xbox 360 client at some point.
That said, if we do offer the game eventually on more than one platform, I'd like to see them share the same world. I don't think there's any need to seperate worlds/shards based on platform or client.