It might be more relevant to look at cases like South Africa, Rhodesia/Zimbabwe or Manchu China: when a small minority is in charge of a country, sooner or later they'll lose power if they can't maintain their viability, maintain a consensus, whatever you want to call it. It worked - up to a point - for the Assads because they managed to keep Syria secular enough that the overwhelming Sunni majority didn't feel truly oppressed. But as I said, after four years of that war, after all the barrel bombs and possible uses of chemical weapons, you can't go back to that point. Assad leads a small minority which doesn't stand a chance of winning the war entirely or even primarily by its own efforts, nor could it realistically maintain control afterwards. If the Russians want to win the war for him and then keep him as a puppet, yes, they can, but that's not exactly an attractive prospect to anyone but Assad himself.