If Doc isnt' coaching, it's a sign that we are going into full-blown tank mode... so it literally doesn't matter who coaches. One of the assistants like Tyrone Lue or something... or hire ML Carr.
It will take us 5-50 years to become relevant again. If that ever happens, I'm sure Doc will have an open invitation to come back to Boston... but he'll likely be coaching some other playoff team by then.