Well, I wouldn’t blame the writers here. I beleive the actor left ER to do another show (Hawaii? Something like that), so he was just omitted from the storylines at the start of this season. Now that his other show has failed I guess he has time to come back to ER.
May sweeps speculation (this is a speculation, I have read nothing, I know nothing…but just in case):[spoiler]He gets shot. For some reason, his injuries are bad enough, and specific enough, that the only hospital that can save him is county. Dies with Neela at his side.
Or because his series was canceled, he gets injured and there’s a touching May sweeps reunion. Next year, he’s doctor in a wheelchair.[/spoiler]