It will certainly be something to keep an eye on in the next several months.
Belichick tends to like a lot of depth at the position, so I can't say I'd be totally shocked if he did end up staying. Of course, he may end up being inactive as the season progressed, especially if the rookies picked up the playbook well, and the team stayed (somewhat) injury free at the position. Just the same, someone may unfortunately get injured in camp, and the decision will be a lot easier.
For those who say that "we need to free up a RB position to make up for the 3rd QB," keep in mind that spot should be freed up by a player who actually DOES PLAY special teams AND a position--unlike Matthew Slater. Yes, we may take a step or two down losing him as a gunner, but the priority should be on being able to utilize the spot with an actual player.
The newly popular thought that the Pats will only keep 4 RB's this year may not be true at all. And if they do keep 5 again, then Faulk's chances just shot way up. My guess would be that he will return for TC, and if he's cut, it will not be until late. Then there's the salary issue to consider too.
I still believe that he could offer good spot playing at times, and be a very good presence in the locker room. A case could be made either way of course.