In light of recent efforts to confuse the bejeezus out of their fans with non-sequels-that-really-are-sequels (ala The 3rd Birthday) and names that border on the unpronouncable (so, is the bracket in [012] silent?), Square Enix has announced Dissidia Duodecim Prologus Final Fantasy.
In other words, a prologue to the upcoming Dissidia game.
Prologus will be released for PSP on the Playstation Network March 15, 2011. Players will take control of Lighting from Final Fantasy XIII, and all items accrued will carry over to the main game on March 22, 2011. Further, purchasing Prologus will unlock Aerith (yes, THAT Aerith) as a support character in the main game.