I think they'd only to do that if there was zero chance he could return before the SB. Realistically who else could be brought up to take his place and contribute on the 46-man active roster.
You just wait and hope he can come back. If he can't then Parnell plays.
I have a gut feeling based on the way this FO has gone about things the last few years that they'll only bring back Free if there isn't much demand for him and they can get him cheap. They seem to deplore paying age. They didn't pay Hatcher last year after 3 straight Pro Bowl caliber years including a double-digit sack year at DT.
I do hope Free gets healthy and can contribute. He has been a major cog in that OL.
Parnell has more upside -- hasn't really been doin this too long, so should be at least equal to Free next year. Already has better upper body strength.
Free would be on IR if he didn't have a chance to contribute, so a couple of weeks' rest and he may be able to go, at least splitting time.
Half of the linemen over 27 in the league have bone spurs; they play through it, and get cleaned up in the offseason.
Free's been a great leader, and may be retained for mixed duty if he gets a good medical report and the price is right.