Square Enix has confirmed Final Fantasy XIII-2 for a January 2012 release in the West. Of course, that's what it's saying for now. This is Square Enix though, so don't rule out the possibility of a delay or five.
Until now, we only know the game was planned to hit Japan in December and Western territories in "early 2012." This is the first time that we round-eyes have been given a firm launch month.
Final Fantasy XIII-2 is the sequel to Final Fantasy XIII. That's why there is a "2" in the name.