These news should be taken with a grain of salt. A different source (German) stressed that the "FFXIII
series" (Fabula Nova Crystallis Final Fantasy XIII) isn't going to be PS3 and cellphone exclusive. It doesn't necessarily mean that there will be ports of the actual FFXIII but that there will be more FFXIII spin-off games than the previously announced.
EDIT:
This graphic shows that both FFXIII and Versus XIII are still PS3 exclusive (at least for now, even Sony CEOs have admitted that it might not be exclusive).