He's been saying he's finished the majority of the The Winds of Winter for about six years
I've been reading a little about the history of Martin's comments regarding book six, and it's been about the same for six years.
He says he intends to finish it but I have my doubts about anything he says about the book at this point.
Seven years ago he was talking about it being months away, or it being likely to come out that year or the next, as if the end was in sight. Last year he said was about 3/4 of the way through it. It doesn't seem like much has changed, really. Maybe he's been doing a lot of rewriting.