They are separate companies, but they have a long standing alliance, and I didn't say none of them would come out for other systems. I have no doubt that spin-offs of all kinds and maybe even a port of FFXIII will appear on the 36 and other systems in the future. It would probably hurt PS3 sales at this stage, because no one with a 360 is going to say, "Hey, I'm going to get a PS3 so I can play that game on it that will also be out in 6 months for my 360." and everyone else will say "I can buy the PS3 or the 360, the 360 is cheaper and it has the same hugely awesome FF games on it the PS3 has, and the 360 is cheaper." I would imagine that Square knows this, and doesn't want to screw with what may be their last chance to rake in some dough on the PS3 without going to other systems, so I think the main FF series will likely, but not definitely, remain on the PS3, at least for the near future. If they experience abysmal sales, sure, they'll probably bring it to the 360.
