This falls into the slowly expanding "what we know so far" category for the freshly announced Final Fantasy XIII-2 .
More details were present in a Dengeki feature in Japan and we've found a rough translation that outlines a few interesting pieces of info. The translation isn't perfect, of course, but it provides us with two very intriguing tidbits: firstly, in addition to the returning characters (which we expected), the story will be "dark and mysterious" and it seems the follow-up adventure will start in Gran Pulse. At least, that's how we're interpreting the following:
"The story begins, according to the developer directly in Gran pulses, the end of Final Fantasy 13th In the center of the action, the deity Etro."
Secondly, the combat system will be tweaked: even though it'll boast an ATB mechanic similar to that of FFXIII, it'll be "extended" and "improved." We don't quite understand what "you may also learn the interface to change" line means but for some reason, we were just reminded of the "changing" of Dress Spheres in FFX-2. …pretty sure that won't happen again, though. Still, a class system might be cool…
More information will come to light as the year progresses. Let's just hope it all goes over well with the fans.
Related Game(s): Final Fantasy XIII-2