Perhaps one of the best games out right now for the PSP is Dissidia Final Fantasy, and with the success of the game, a sequel is on its way, titled- Dissidia Duodecim Final Fantasy.
According to Shonen Jump, Final Fantasy XIII’s Lightning and Final Fantasy IV’s Kain will be playable characters, which is the only information we know of for now.
This new Dissidia is probably the mystery game Tetsuya Nomura said will be playable at TGS, so expect some more info or perhaps a trailer when TGS arrives.