Final Fantasy XIII is definitely going to stay a PS3 title, a 360 port is iffy at best, but remember there were technically 3 main final fantasies released on the same platform during the last 4 generations, if the PS3 doesn't pick up sales sufficiently even with Final Fantasy XIII, then seeing the other 2 for this generation appear on Wii becomes an excellent possibility.
Nobody is crazy enough to accuse me of being sane.