I could be 100% wrong but I think he will only be around a year or two until he can find a DC job or get back to the NFL.
As for taking over if Tony White leaves I don't know if he's the guy. He only has one year of P4 DC experience with O'Brien at Penn State.
His own high school friend McDermott didn't hire him for DC at the Bills and that's the reason he left after six seasons.
I think Rhule will end up promoting one of the younger guys to DC Dvoracek? before he promotes Butler.
Like I said probably be a good position coach for us for a year or two but I wouldn't expect too much more beyond that.
My real concern here is recruiting he hasn't been in the college game for ten years and obviously a lot has changed.