It’s already taken Martin that long to complete this part of the story, and if the author wants to keep living up to the expectations of his fans, he’ll have to put even more effort into the next one.
And looking at the calendar, that would be a borderline impossible feat. With that in mind, is it possible that Martin could be considering to cut the story short and end it at “Winds of Winter”?
It’s hard to say how his fans would react to that, but it’s probably safe to assume that many would be disappointed. No matter how the author concludes the story (if he decides to conclude it in “Winds of Winter”, that is), it will likely feel rushed to most of his fans, and they will be skeptical that this was the right outcome.
It’s also possible that Martin could give the rights to the series to someone else who can finish the story, but that will open an entirely different can of worms altogether. We’ve already seen how this tends to work out for other authors, and the result is rarely pretty. In most cases, it’s impossible to live up to the standards that the original writer has set, no matter how much effort the new ones put into their own work or how many fans they already have.