A SONG OF ICE AND FIRE will eventually run to six books, so I still have three and a half to write. That will keep me busy for quite a few years.
After that, there's no telling what I'll do. If I do eventually write a prequel to ICE AND FIRE, however, it will not concern the overthrow of Aerys II. I'd go back earlier than that, and follow up with Dunk and Egg from "The Hedge Knight."