The decision won't be Fulmer's to make. He will be in the unemployment line too. His AD power play combined with an incompetent hire will have made enough of the right people angry enough to see them both gone.
If Tennessee goes 1-11 or 2-10 and Phil does nothing that shows that he cares more about his hire Jeremy Pruitt than he does about the Tennessee football program and he should be fired after Jeremy Pruitt is finally canned.