I thought Beamer's retiring was not a big surprise, and that there's a HC-in-waiting on his staff. But I have no idea why I thought that....
For a long time there was speculation that Bud Foster would be in line for the job if/when Beamer retired. I can't recall whether he's had serious suitors for other head coaching jobs, but I would think it's no accident that he is the highest paid assistant coach in college football (makes something like $1.3 million/yr). That said, he's been an assistant so long that his window of opportunity may have come and gone (he's in his mid-50s now, not terribly old, but older than most coaches get their first shot at a HC job). More recently Beamer's son has been the rumored successor.
Officially I'm pretty sure the NCAA did away with the "coach-in-waiting" title a few years ago, but that doesn't mean that you can't unofficially have a succession plan in place.