Yep.. from his recent 60 Minutes interview:
“Anderson Cooper: When it was clear they were catching up, you told them a kind of an overarching future of where you saw the last two books going in terms of plot?
George R.R. Martin: Yes. And, you know, the major beats. I mean, obviously, we're talking here about a-- several days of story conferences taking place in my home in Santa Fe, New Mexico. But there's no way to get in all the detail, all the minor characters, all the secondary characters.
Anderson Cooper: I mean, do you worry that some fans will have Dan and David's ending in their mind's eye? Would that be a disappointment to you?
George R.R. Martin: I don't think Dan and Dave's ending is gonna be that different from my ending because of the conversations we-- we did have. But they may be on certain secondary characters, there may be big differences. And, yeah, some of the people will have that. There will be a debate, I'm sure. I think a lot of people, who say, "Oh, Dan and Dave's ending is better than the one George gave us. It's a good thing they changed it." And there will be a lot of people who say, "No. Dan and Dave got it wrong. George's ending is better." And they will all fight on the internet. And there will be debate. And-- that's fine. I mean, it-- you know, the worst thing for any work of art, be it a movie or a book is to be ignored. (LAUGH)”
https://www.cbsnews.com/news/how-wi...e-of-thrones-books-end-60-minutes-2019-04-15/