All I've seen is there was an episode or 2, where he was shot, then the re-occuring role of the lady Social Worker was killed by a young girl in the precinct office and I think Stabler had to shoot her. It was a major episode or 2 about the ability of kids to get a hold of guns from the streets. I believe it was a season ender and he was "suppposedly" on medical leave and then made a decision to not come back. I saw the episode when the Chief told Liv that he wasn't coming back and she went in an interrogation room and broke down crying. Next episodes show various new people on the team and she is very cold to them. Also when the new season starts, Liv is going to have a "love interest" played by Harry Connick, Jr.
Don't think I will like Elliott as a blood sucking vampire! JMHO