From what I understand, he's working on several different projects in parallel, including "The World of Ice and Fire" (companion), "The Lands of Ice and Fire" (map book) and "Tales of Dunk and Egg" (novella). He continues to write/consult for the show and he recently finished up assisting the creation of the RPG video game. He's a busy dude.
If he concentrated entirely on finishing up the main books then I think he could make it. If he keeps sharing cycles with these other projects, though...I dunno...