Jimbo would owe buyout for his coaches contracts, approximately $7M. That is if none of them are retained. Judging by their recent performance I doubt any of them would be. If he got fired he would be owed $39M right now.
Sometimes guys want a change, or sometimes their message gets stale and they can sense it. These guys will jump ship before their stock and reputation takes a bigger hit than it already has. See Urban Meyer leaving UF as an example. Jimbo also had to deal with an embarrassing divorce there.
Not saying he leaves, but there are reasons he could consider it. His agent has literally done this almost every year since he won the NC though. If he get him a raise after this disaster of a season that is impressive.