Square Enix has announced plans to release a new PSP game titled Dissidia Duodecim Final Fantasy.
According to Shonen Jump magazine (as read by Andriasang), it's due out next year.
Lightning from FFXIII and Kain from FFIV will be playable characters.
Apart from that, nothing is known about the game. Seems likely more will be revealed at next week's Tokyo Game Show, though.
The original Dissidia: Final Fantasy scored 8/10 on Eurogamer last year. Have a look at the review for the full banana.