I think Doc is waiting and seeing what happens with PP and Kg, he is very attached to his two veterans, and their relationship with Rondo is not the best,
It's all a mystery that will happen, but something must be happening to Doc not decide if he agrees to come back or not. I think he has doubts if Ainge can form a competitive team, this added to the uncertain future of PP and KG, see what happens, I guess in the next few hours or days there will be news about Doc first.
There are many rumors, but no one says anything true, many opinions but do not know anything, much speculation.