First, Michigan has to accept that the only path for them to beating teams like Bama and Georgia is to have a sizable advantage at QB. That's the only way anyone else has ever won. Watson, Lawrence, Winston, Newton, etc. You aren't going to win because you have a better roster. You will win because you're good enough everywhere else and you are significantly better at the most important position.
So then, they have to be happy winning the Big Ten somewhat regularly, making the CFB playoffs when that happens, and generally being a very good program. I have no idea if the fanbase can accept that but it's the reality. Anyway, I think there's a plan for Gattis to be the guy barring unexpected interest. That's what I'd do if I were them as they have, IMO, one of the best staffs in CFB at the moment and breaking that up is a bigger risk than hiring a guy like Gattis who's been around really good coaches for awhile and seen a lot of different ways to run a program. I'd be moderately surprised if Campbell was interviewed.