I'm not as high on Kubiak as you are, but maybe so. But for that to happen McCarthy would have to significantly change his offensive scheme from a traditional West Coast system to the Shanahan/Kubiak system. Not sure he would want to do that.
It's hard to know what we have in Kubiak due to the injuries and DA's utter and total incompetence.....but my feeling is that if the new HC is anyone other than Rizzi then Kubiak will go elsewhere......