I am sorry for saying this, but looking at GRRM's health and how he works, we are not going to see the end of the books. At least not by him. His productivity (whatever little there is) is only going to decline as he ages.
I wouldn't go that far but one thing is certain: he will not finish the books unless he changes his behavior, and to be frank I have no reason to believe he'll do that. Martin deserved to take a victory lap after ADWD (during the press tour). But instead of getting back to work in 2012 he once again stuffed his schedule. IIRC by 2013 he had around 400 pages of TWOW, half of which were originally from Dance.
Let's assume (lol) that Winds comes out next year, say in the spring. So all year will be the book tour, and then I guarantee you in 2018 he'll once again have more conventions, more appearances, etc pumped in.
I get it, he likes cons and probably knows he doesn't have much time left to attend them. But at some point he needs to decide to sit down, write, and only attend a couple events a year. But he won't so....