Let me clarify something right away..
If Jim Harbaugh leaves Stanford for the NFL, it will be for a Head Coaching job ONLY.
There's a zero percent chance he'd leave Stanford to become the Offensive Coordinator here or anywhere else for that matter. He'd be taking a major step backwards by doing that, and frankly Harbaugh is better off staying at Stanford and continuing to build that program into a Top 10 one than to go take a coordinator job in the NFL.
You want Harbaugh to come to Glendale, you're gonna have to offer him something higher up the ladder than coordinator.
Truth be told, I don't think Jim Harbaugh sticks around at Stanford this off-season. I'm almost certain the Vikings will make a run at him, and I really wouldn't be stunned if Cincinnati and Carolina get in on the chase, and could offer the possibility of some moderate control. With the possibility of him being able to get his college QB and a guy he groomed on the next level, this might be enticing to Harbaugh. Also, if Dallas hits the skids, I wouldn't be shocked if they at least offer Harbaugh an interview.
I also am convinced Michigan is going to move on from Rodriguez and will go hard and heavy after Harbaugh, and UM would be an extremely tough job for him to turn down. Minnesota already has let it be known they want him.
He'll have plenty of head coaching offers this off-season, trust me on that.
Regarding Luck, I've sort of softened on my stance that there's no chance he returns to Stanford, when probability of him being the top overall pick is so likely. I DO think there's an outside shot he could return for another season in Palo Alto. If Harbaugh returns there, Luck could want to return to try and make a run at a National Title, which could be realistic in 2011, and that may motivate him to go back for another run.
As is, I'd say his chances of returning to college are about 20 percent at this point. There's a chance, but I don't see those chances being very good.