Teams havent been hiring DC's for their head coaches anyway.
This. It's an offensive league and if you look at the DCs hired as head coaches the results are mixed, at best.
I'm hoping he stays obviously, but everyone assumes he'd jump at the chance to be a head coach and that's not necessarily true. Not everyone is a ladder-climber. Maybe he likes what he does and where he's at and maybe his family is happy being here. Nobody knows.
Life isn't always about moving up and increasing your power and control and wealth. Some dude's are happy at a certain level of success and don't want to F with it.