I have it on good authority that his editor does very little, and that part of the issue with his books coming out so slowly is because his writing method involves hunt and peck typing on Wordstar, and that he meticulously edits his own writing to the point that his own editor waits eons for very few actual editing decisions.
^ Wordstar.
All in all, some of us remember the blog messages about taking time out for the NFL season, about how he did so much damage to the Starks that he wrote himself into a corner, and yet he's added 8 books to his bibliography since A Dance of Dragons and had executive produced another television series (Nightflyers).
As far as I see it, the guy's fiction legacy is now competing against another product (GoT on HBO), and the HBO show has become more popular than his novels. Since the HBO show is allegedly going to have a different ending from his novels, both are ultimately going to be paired up against each other and my guess is the TV show is going to win.
If his novels suck, it would damage the TV show, which I venture he's making more money on than he stands to make from his books. He's 70, has never seen this amount of money and attention, and is definitely overweight and (per my convention friends who spent some time with him) there isn't a pizza that he doesn't like.
Verdict: He doesn't have a Brandon Sanderson lined up and he's coasting on the money while he has a chance to live it up.