I'm just convinced that GRRM doesn't know how to end stories. He's never done it before. He wrote for a lot of TV serieses (Beauty and the Beast, Twilight Zone, Max Headroom) that didn't have "endings," they just got cancelled.
He knows how it's supposed to end, he's publically said however that he has no real plans for how it gets there outside of vague roadmaps in his head. If he died right now, and they tried to circumvent his wishes, no writer would have any more to go on than HBO does. It does not compare to Jordan who literally had notes upon notes to the point that the last book had to be split into 3 books and there were still things left out.
Yeah, that's where we disagree, he clearly has a lot of plans about how to get there, he just keeps changing them, and changing them... that's why he could be think he'd be able to finish a book in 6 months and then take another 4 years. Or how he can be at 600+ pages in 2008, but not finishing the rest 700+ for said 4 years.