Heading up college and pro team have really diverged in the last 25-30 years so citing anyone outside of that time frame really doesn't make any sense. I would think there are really only two you can cite: Carroll and Mora(and to a certain extent the jury is still out on Mora). O'Brien really doesn't count because he actually has more college experience than he does pro experience.
That isn't to say that there is a pro guy out there who could be successful at the college level but it would have to be as rare an occurrence as has already been witnessed. Sort of like the # of successful short qbs in the NFL as in once in a blue moon.
Whenever Kelly is replaced, the guy will come from the college ranks or a guy like Harbaugh/O'Brien who has extensive and recent college experience.