George R.R. Martin drops massive clue about the new 'Game of Thrones' spinoff

one

adaptation

"I can say that, like the other pilots, it will be a prequel rather than sequel, a successor rather than a spinoff. Bryan’s series will be an adaptation, and one that will thrill most fans of the books, I think, set during a very exciting period of Westerosi history. And I’ll be working with him every step of the way; we’re going to be co-creating the show."

"He's written more episodes of Game of Thrones than anyone but Dan & David [DB Weiss and David Benioff, Game of Thrones showrunners]... including some of our very best ones. If D&D have been the kings of Westeros for these past seven seasons, Bryan Cogman has surely been the Prince of Dragonstone. I'd love to tell you more about the series Bryan will be working on... but we haven't done that for the other four successor shows, so we shouldn't for this one either. All in good time."