I've always thought that there's a lot of undue vitriol being spewed his way by fans. I'm sure most of them would flip if you told them they had to stop having hobbies and go work sixteen hours a day. Heck, most people get grumpy if they have to work ten! The bottom line is that GRRM doesn't have an obligation to his fans to work 24/7 simply to appease their desires. The fans did not make his career - he did that by writing (some) good books.
However, that said, as time has passed I've fallen into the camp that thinks GRRM simply isn't interested in Ice and Fire anymore. This post seems to me to back up that line of thought.
Regardless of if this is the case, he needs to stop whining and accept the consequences of the bed he made. Boo hoo, you became famous... suck it up. It's been four years and four months since the last book came out. If you want your fans to stop bitching, finish the book or tell them it's not being worked on.
Then again, I would never have gotten through even the first book without the help of audio tapes. Entertaining to be sure, but the insane popularity is overrated IMO.
So, George, futz around and pull a Douglas Adams on us. We've made you wealthy enough never to have to type another line again, but you never signed a contract obligating you to actually finish your work. As always, a sense of entitlement is a dangerous delusion.