Stevens will either retire on his own, or God will retire him. Hard to say which will come first.
I don't know why we are getting our hopes up for this to happen. Look at Strom Thurmon. He lived until 100. We may have 15 years of Stevens to go. I don't count the chickens until they hatch that way you are never disappointed.
Stevens and Ginsburg will die in office. Tyrants and Communists do not give up power voluntarily under any circumstances, and they are both.