Fisher isn't going to college, and there are several reasons for it. He's one of the highest paid coaches in the NFL, and currently one of the most winningest, so if he were to leave the Titans, he would likely move on to another NFL gig. He's never coaches in college before - not even as an assistant. He went straight from a DB for the Chicago Bears to helping Buddy Ryans as a player assistant - been as assistant, coordinator, or head coach in the NFL ever since. He's never had to do the recruiting thing, or build/maintain a collegiate program.
I just don't see this happening. It'd be a pipe dream for USC fans.