Ray's a freak, he made it clear following the game he wouldn't end his career with an injury. If you watched the special they had last week where he talked about knowing when to quit (He subsequently took shots at Favre) he said he had another year left in him. He'll be back next season.
Ray's the emotional & spiritual leadership of this team, not just the defense but we played pretty damn well without him during that stretch last season. Ngata & Webb concern me a crapload, especially considering the fact that Webb has been one of the most underrated defenders in the League & Ngata's the anchor for that line.
According to USA Today, the only way it ends his career is if he chooses not to undergo the surgery & endure the rehab. It's not a 'Can't', he would have to choose not to undergo the surgery.
Guy just totally overhauled himself in the off season just to streamline himself, he's more than capable of doing what's necessary, it's just a question of whether or not he finds it to be his time. If he felt that he couldn't get back to where he wants to be, then he'll say so.
For your everyday Joe, a severely torn tricep takes 4 - 6 months. With Dr. Andrews & the trainers / regiments available to professional athletes, I'm sure that time could be cut down but since he's already out for the season, he could easily recover in time for next season, if he's willing.