Dollars to doughnuts, they each have acquired new, younger, more attractive squeezes. Seems de riguer of the billionaire class, cf. Warren Buffett, Sergey Brin, Larry Ellison et al., and their respective wives. To their credit, Bill & Melinda Gates seem to be sticking it out.
Word around the campfire is Bill had a clause written in to deal with just that issue. He essentially gets a structured pass, if you will.