I've faced reality, long before just now. We may get winds of winter, but it is with solemn certainty that I say we will not get the last book.

Grrm is either incapable of delivering an ending, or just doesn't want to. I think it's a combination of factors, but his biggest fault is his self titled gardener writing style. He planted too many seeds and failed to prune and harvest. He is left with facing down an overgrown garden. If he had kept up with things, trimming here and weeding there, as he went along it wouldn't feel like such an insurmountable task, yet here we stand.

I doubt he could finish the story in two books, but even that is too many. He is getting older, his pace has slowed and the distractions grow ever more tempting. He is faced with an overgrown landscape and realizes that he does not have the time to tame the beast.

Thank God the TV show will give us something of an ending, otherwise it would just be blue balls to the end.