A Game of Thrones question

Rewatching Game of Thrones on HBO got me to wondering about the books. Specifically, how can George RR Martin possibly (1) bring Jon Snow back to life, (2) have the Others become a major plot element (presumably by attacking the Wall), (3) get Daenerys onto the Iron Throne and her dragons up to the Wall in time to defeat the Others, not to mention wrapping up a couple of hundred other plot elements in just two more volumes? Given how slowly his plots move, that looks like at least 5 volumes worth of material to me. If Martin really is going to pull a Robert Jordan on us, maybe he should start prepping Brandon Sanderson to finish the series in case something happens to Martin?