In one of his newer blog posts, author of A Song of Ice and Fire, George R. R. Martin mentioned that three of the originally mentioned five spinoff series are still “moving forward nicely.”

The one I am not supposed to call THE LONG NIGHT will be shooting later this year, and two other shows remain in the script stage, but are edging closer. What are they about?  I cannot say.  But maybe some of you should pick up a copy of FIRE & BLOOD and come up with your own theories.” The series that Martin is apparently “not supposed to call The Long Night” is a prequel series set thousands of years before Game of Thrones. The series is written by Jane Goldman (Matthew Vaughn’s go to screenwriter) and is starring Naomi Watts (Mulholland Drive, Birdman). Here’s the series’ official logline as released by HBO: The series chronicles the world’s descent from the Golden Age of Heroes into its darkest hour. And only one thing is for sure: from the horrifying secrets of Westeros’ history to the true origin of the white walkers, the mysteries of the East to the Starks of legend… it’s not the story we think we know. What I find particularly interesting is Martin specifically mentioning Fire & Blood. The book was released late last year and covers in depth, the history of House Targaryen. Could this mean that the Targaryens are tied in some way to the creation of the White Walkers? Just thinking about it makes my gears spin! (Source: George R. R. Martin)

Game of Thrones Spinoff Could be About Targaryens and White Walkers - 97