Demoff will have nothing to do with Fassel. Whatever HC that is chosen will choose his coaching staff and will have to decide if Fassel is a coach he wants on his team.
You aren't going to hire a HC by handcuffing him to unwanted staff.
True. Then again why would an incoming HC not retain one of the best ST coaches in all of football? It's actually quite common that while not a requirement that a GM would like to see certain coaches kept on especially if they weren't part of the problem and can be part of the solution going forward.
I dunno what will happen, but I know I'll have very little patience for bad ST play after Coach Bones.