This seems like a no-brainer for him. Look at his history:
He starts out as a graduate assistant working for Saban. Then he works for the Patriots from 2000-2006, learning from the best pro football coach in the game. Then he strikes out on his own, and is OC for the Browns, Dolphins, and KC from 2007-2012, and he doesn't really light the world on fire at any of those places. Then, back to school with the Patriots from 2013-2017, another stint with the best pro football coach in the game, but as a TE coach instead of a OC, a major step down from his previous positions.
Now he becomes OC for Alabama under Saban, the best college football coach in the game and the guy he started out with. Talk about burnishing up your resume! A year or two as Alabama OC, maybe a national championship. Seems to me like he would be pretty hot property for either college or the pros after that with his experience under BB and Saban, no? I could see many teams interested, maybe even the Pats at some point down the road.