I predict that he will not be acting coach by end of season. He knows now his recruiting (lack of) has failed him and his coordinators are hindering his plan to win and hand the program to Sean. If he had contended for a confy he would have had a decent chance to get Sean in. Now, Dimel and Miller are hurting Sean's chances.
So, Bill fakes an illness or pretends he is too tired to keep going, he installs Sean as interim just in time for the softer part of the schedule in hopes he wins some games then makes the push.