Putin being deposed is the optimistic scenario, but I don't see it as the most likely one. He's pretty insulated from external attack, and he has internal dissent pretty locked down at this point. Hitler wasn't finished until the allies were rolling into Berlin. He fought off coup attempts well after it was clear the war was lost. Putin isn't going to be under nearly the same level of external pressure. Honestly I expect it's most likely the world is stuck with him until aging and/or disease make him unable to rule. Hope I'm wrong, of course.