FF Versus 13 isn't going to go multiplat.
I see too many parallels between MGS4 multiplat rumor's and Versus XIII ones......EVEN A EXECUTIVE of Konami said in TGS 2007 or before that that they were considering a Xbox 360 version of MGS4.....nothing ever came out of that.
Not only this FFXIII on PS3 will end up selling 5 Million overall....thats just 600K below FFXII, FFIX, X-2 which were all on a much bigger platform with marketing for that platform unlike the multiplat release and zero marketing FF13 (PS3) got in the west.
PS3 is strong enough to support a Final Fantasy game on its own shoulders and if you actually read news about Versus XIII since the past many years you would know it is difficult to port the game.
A better question would be -- Will FF Agito XIII go multiplat to the 3DS at the January Conference?
That would be a more relevant and a better question because I wouldn't want to release what is most likely going to be the most expensive portable game of all time on the PSP exclusively......in 2011 when the 3DS will be blowing up the charts and PSP 2 will have been revealed.