Some massive overreaction to the Wade Phillips departure, IMO.
The Broncos' defense is now in its inevitable decline - regardless of Wade. They were terrific for 3 years, likely will still be quite good next season, but these sorts of things don't typically last very long in the NFL.
They lost two good starters last offseason, they'll lose at least one more this offseason, a couple of guys are getting close to 30 (when they'll start to decline), and the team really has to focus on the OL early in the draft (I would think, given the state of the OL). Throw in a moderate injury or two, and they're going to likely move down from an elite defense to just a good one.
A lot of fans will be screaming "Wade! Wade!" when this happens, but that won't be the real reason.
Besides, Joe Woods has a very good reputation coaching the defensive backfield - one that has been really good for Denver. If he were promoted, it would provide continuity.