I think it's in Square's best interest, in Japan, to make XIII multiplat.
Why? They already have a litany of JRPGs on the X360 already, and coming - TLR, IU and SO4 is coming. If XIII was there, they would improve sales of the 3 titles, as users look into the X360's back catalog of JRPGs. That's compared to the Playstation 3 which has absolutely no Square-Enix JRPGs as of yet.
Back from the dead, I'm afraid.