I have been convinced that he will leave for some time and winning the National Championship makes it almost certain. (IMO, of course.)
Also IMO, the suspensions themselves are inconsequential to his decision, but the still-open NCAA investigation is a prime driver here. The big one is not the Connor Stalions episode, it’s the largely technical infractions that Michigan already agreed to prior to the season. But the NCAA Committee on Infractions rejected the negotiated settlement and is accusing Harbaugh of lying to them during the initial investigation, which is a Level 1 infraction. (This is the infamous “cheeseburger” story, where he was asked about buying a recruit an impermissible meal during a recruiting “dead period” three years ago and said that he did not remember.)
If Michigan wants to fight the level 1 charge, they will almost certainly win. But that will take years and I can’t imagine Harbaugh wanting to spend any time dealing with that when he can wash his hands of it by heading to his choice of jobs in the NFL.
BTW, this is the “short version.” There’s a lot going on. So I think he leaves. (Hell, I would.)