I can't say that UTK's progression above the mean is guaranteed, either. Historic success != future success.
Fair enough. That being said, maintaining success at a school that hasn't had much historically is much more difficult than restoring success at a program like UT. I think the difference is built in institutional, alumni, and fan support.
Consider programs that traditionally aren't "power programs" but have/had recent success:
Stanford, TCU, Baylor, Vanderbilt, Rutgers, Boise State, South Florida, Kansas State.
Who has had sustained success after the "architect" leaves? Stanford and Boise State; though, Boise has fallen off and it looks like Stanford is slowly drifting backward.
Who regressed immediately after the "architect" left? Vanderbilt, Rutgers, South Florida. Kansas State would fall into this category too.
It'll be interesting to see what happens at Baylor when Briles leaves/retires.
The point is that UK is punching above their weight class. Stoops is a good recruiter and is proving to be a really good coach. If/when he leaves UK, will they stay up or will they regress. I think it's more likely they regress, especially if Stoops stays for 4 years or less.