The idea that we're going to be worse if/when/because JB leaves is silly.
1) He is going to leave, at some point. So, where we go from there is largely irrelevant in terms of how much you love JB. Fact is, we are where we are with JB, and it's doubtful he's going to get better in the few remaining years he has left.
2) We just lost to a bunch of teams with coaches i could not even name during the games i was watching. If those schlubs could beat us, with less legacy, fewer/worse resources and facilities, and probably less HS talent, i'm not sure what it would take for us to be better from a coaching standpoint.
3) Coaches don't tend to get better and better through the entirety of their careers. There's an arc. We're not at JB's peak.
4) If you're thinking we currently have a HoF coach, and replacing him means picking from a pool of dudes who are not likely to also reach the HoF, your thinking is flawed. The current HoF coach is not performing at HoF levels. We don't have to replace him at HoF levels in order to be better than we are now. The point isn't to compare an incoming coach with what JB accomplished over the sum of his career. Or even the average of his career. We have to have someone do better than what we are seeing from JB right now.
The story might be different if JB were 60 now. With all he has done, you probably give him leeway, imagining he would evolve during the next 15 years. But, he was already scheduled to retire. He will be retiring soon. There's no space for him to fix all that is wrong.
My only worry about JB retiring concerns how much of his 'residue' is left behind. Does the house need to be cleaned? I have a feeling that Hopkins winning Coach of the Year out west will inspire the admin to just fall back on another one of our own, expecting the same kind of 'success.'