Between the ascension of Romanovs (1613) and Gorbachev, only one Russian ruler left office any way but feet first, and that was Krushchev. With Putin having taken Russia back into the same repression/corruption/stagnation status that has pretty much been its tendency for all but 20 years of the last few hundred, I guess we have to assume Putin is there till he dies, at which time he will probably be replaced by someone from the small cohort of similarly aged ex-KGBs that have stayed in his immediate orbit. Much like when the last of Brehznevs the post WWII group passed from the scene, only at that point are we likely to see an opportunity for another Gorbachev style generation shift and an opening for reform. Maybe it will last more than 20 yrs next time.