I fully expect Cal to stick around another decade or so. He'll be 57 this winter, which is young by elite college coaching standards. K is still going strong at 68. Izzo will be 61. Pitino will be 63 in September. Roy turns 65 in a few weeks. Boeheim turns 71 in November. Calhoun was over 70 when he retired.
If Cal sticks it out until his mid to late sixties, I think UK's success rises to an even higher level (hard to imagine, but K being retired at that point will make Cal college basketball's elder statesman). He'll have the "old wise man" appeal that Calhoun had and that K currently has. Plus at that point, he'll presumably have around 30 guys actively playing in the NBA, and perhaps a few more Final Fours stashed away in his pocket.
I mean, people have to remember that trumping even Cal's passion for the game is his love for communicating. UK offers that platform unlike any other coaching job in the world. I think he knows that and loves it, and it is in part why UK has survived a second summer of LeBron's whimsical impulses and kept Cal around. Plus, it's clear he gains a sense of continuous, positive motivation with every new NBA green room filled with UK guys. He feels like he's changing the world on some level, and I think we see him at UK for the long haul as a result of all these factors.