The only thing I've heard confirmed is the themed space and stuff for PlayStation Home. (No word on the 360 version, which features the Xbox LIVE logo on the cover.)

If I had to guess, I'd bet that there will be some modular content released, in the form of some extra (optional) battles. I'm not that far into the game yet, but there's supposed to be a hub area later in the game where you can grind for experience, or battle creatures that are supposedly tougher than the enemies at the end of the main storyline.