Unless he loses like 5-6 games including to OSU for the next couple of seasons his job is fine. He's been giving them 10 win seasons fairly consistently and major bowl appearances (albeit mostly losses but they historically lose more bowls than they win-even their greatest coach had a losing bowl record)and that's a sight better than what happened during the Rich Rod and Hoke eras. In fact, that's pretty much par for the course for Michigan teams in the modern era In the last 40 years their ceiling is usually being a 10 win program that made noise on a National Championship level once. All he has to do is keep that going and he'll be fine. Beating OSU once in a blue moon is a great bonus but they'll settle for being competitive every year if it comes to it. Besides, who could they hire right now that could do better, realistically?
The Harbaugh era at Michigan is what Michigan is. Their problem was the fanbase let their expectations get out of control when they hired him, thinking he'd be the next Saban or Meyer there. They seemed to forget that they are Michigan and football dynasties are really really hard to come by, even for the bluest blood.