I think both should be let go tbh. Kaep isn't going to get much better. With respect to Harbaugh there's a reason he doesn't really stay anywhere long. That locker room is clearly tired of his antics, as is the front office; he's a guy that just burns shit down to the point it gets grating.
I think Harbaugh will go somewhere where he's given the control he demands. He can get that in Oakland or perhaps NY (Jets), where he could be a coach/GM. Or he could go to Ann Arbor and have complete dominance of the Michigan program/highest paid coach in the NCAA.