Much like college players, coaches are always keeping their ear close to the NFL door and keeping an open mind about possibly leaving for the professional ranks. The NFL usually pays more, allows a little more freedom and is considered the peak of football coaching.
While your favorite coach is currently saying how happy he is at said school, you better believe he wouldn't think twice about leaving for a better job opportunity. Coaches change gigs all the time, and if it means a fatter paycheck and more notoriety, see ya!
A lot of the time, NFL franchises like to go with the latest big name in the college level. It would help if he had some NFL experience, but swinging for the fences and landing that big fish is what it is all about these days.
The good news is that there are some popular names that will soon be on the market.