A very close look at the job descriptions seems to suggest that a possible God of War multiplayer title could be what the studio is thinking about doing. Of course, this is just a guess, but other places are also onto our way of thinking about this based on what the job descriptions suggest.
No word when Sony might be in the position to announce what the Santa Monica studio is working on, but the suggestion that they could be talking about it next year at E3 would not be far-fetched.