Square Enix made formal announcement today of something we reported on last week courtesy of Jump. Dissidia Final Fantasy is getting a sequel, and it's going playable at the Tokyo Game Show later this week.
Incidentally, in our headline, we wrote the name as Dissidia Final Fantasy 2 in order to avoid confusion. But you're probably already confused beyond repair. Blame Tetsuya Nomura for that!
Duodecim will add new characters, new maps, new BGM, and new battle system elements to the Final Fantasy crossover fight. A whole lot of new features, to be sure, but we only know of two specifics: playable Lightning (from FFXIII) and playable Kain (from FFIV). Square Enix assures that there will be more new characters than just these two.
taken from http://psp.ign.com/articles/111/1119821p1.html