Mega-writers Jordan (of Wheel of Time) and Martin (of Song of Fire and Ice) get a lot of flak for the rate they release their books: years pass between each book. (Jordan, of course, gets flak because his books are terrible. Zing!)
Have you tried to write a book? Do you know how long it takes? Have you experienced the days where you have no idea what to write next, even though you have the plot lined out, the words won’t come to mind? Or perhaps you’ve drawn a complete and utter blank on plot. Have you tried proofreading your work? The first draft of anything is crap, and proofreading a 500 page novel is going to take a whole ton of time.
So yeah, that next fantasy blockbuster is going to take a while. I know what it’s like to be a writer, and you can’t rush creativity. You just have to write when the iron is hot.
So cut Martin some slack. He wants the book to come out as much as you do, possibly more since it means he gets paid. (You may continue to chide Jordan, but only about his actual writing, such as the increasingly terrible pacing, and the lack of any sympathetic characters.)