I don't think there is going to be a XIII-3, the cliff hanger ending is more likely a prelude to DLC then a full sequel. SE wouldn't dare do XIII-3, the amount of damage it will do to the franchise would be ridiculous.
Whats FFXII team doing right now? Maybe we could see a FFXV announcement at TGC this year, with vXIII arriving in japan in the fall and over here by march 2013.