These rumours are going to persist as long as keeping the games exclusive is going to mean SE and Konami stand a good chance at losing lots and lots of money. Everybody denying loss of exclusivity doesn't really mean much here, because denying stuff like this for ages and suddenly doing a complete turn-around, or even publishers deciding to have another team port the game without asking the original developers is pretty normal in the gaming industry.
FFXIII looks like it's going to be late 08 for Japan and 09 for the West, so it's the more likely of the two to remain PS3-only. The franchise also sells the most in Japan, and while the PS3 is doing horribly there, the 360 is still far weaker.
MGS 4 might actually launch as an exclusive, but making the inevitable remake that comes out in a year a multiplat is a complete no-brainer for the suits in Konami. It's important to note that at least 3/4 of the sales of all MGS titles have been outside Japan, so the 360's weakness there isn't much of an issue.
I don't see either one of them being ported to the Wii as likely, although they'd probably sell pretty well if the ports were decently done, and not released too much later than the originals.







