According to Sony, the PSP edition of Fat Princess, subtitled Fistful of Cake, will see a UMD and PSN release on April 27th. Fistful of Cake is also bringing an expanded single player mode, as well as more game modes for massive multiplayer action.
One factor that was not brought up was how much the game will retail for. Apparently the price has yet to be confirmed, but it will be curious to see how much this update of a PSN title will run for.
Either way, this makes for a great game to come out on the PSP, as long as it's anything like its PS3 counterpart.