P.S. You'll see at least one spin-off
HBO closed deals with five writers -- Jane Goldman, Brian Helgeland, Max Borenstein, Carly Wray, and Cogman -- to explore ideas for Game of Thrones spinoff and prequel shows and work alongside Martin with world-building. Just don't expect to see them onscreen immediately. "You're not going to see a situation where the next show in the Thrones universe launches off the back of this one," Bloys told EW. "The show that Dan and David have created will get its proper send off first. We wouldn't want to take away from that in any way."
And don't expect any of them to be continuations of, say, Ae(Jon)'s exploits. "Every episode of The Naked City -- one of the television shows I watched as a kid -- ended with a voiceover: 'There are 8 million stories in the naked city,'" Martin said. "There are 8 million stories in Westeros as well… and even more in Essos and the lands beyond."
That being said, the first of the forthcoming series, a prequel, is set to be led by Naomi Watts who plays a socialite with a dark secret in an era preceding GoT, seeing the fall of the Age of Heroes. As Game Spot pointed out, if the season will actually cover the demise of the Age of Heroes, it’s likely to give more context to the White Walkers origins. In fact, Martin accidentally let it slip that the season may or may not be called The Long Night, which Game Spot notes refers to a long, horrible winter that ravaged communities and saw the arrival of the White Walkers for the first time in Westeros. Meaning if that is the title of the show, that and a whole lot of White Walker drama is likely the plot.
One more caveat: "You should not expect to see all five shows" at once, Martin added on his blog. "Much as I might love the idea, HBO is not about to become the Game of Thrones network," he wrote, "but we could possibly see two or even three make it to the pilot stage, with one series emerging on air in 2019 or 2020… and the others maybe later, if they come out as well as we all hope."
Though little information has been confirmed about the spinoffs’ plots, we do have a vague idea of what they won’t be about. Martin shot down speculation that the shows will wind back to Robert’s Rebellion, which has been alluded to throughout the series, and that it could focus on his Fire and Ice companion novellas, Dunk and Egg. He took to his blog to clarify, "When the day comes that I've finished telling all my tales of Dunk & Egg, then we'll do a TV show about them, but that day is still a long ways off."