While Game of Thrones is not ending after next season or even after next year, we are reaching the end of the long-running drama, which will air its final episode as Season 8 wraps up. Because the show is getting close to ending, many fans have wondered whether or not HBO will sign on for a sequel or a prequel to the popular drama, which is based on George R.R. Martin's popular books. There are plenty of stories that have yet to be told in the Westeros universe, but HBO isn't 100% in yet. Recently, HBO Head of Programming Casey Bloys revealed that the idea may have not come to fruition, yet, but it isn't dead either:
I would say it's still kind of preliminary ongoing talks. There are areas we are exploring, but I wouldn't point to any one and say, 'This is what we're going to do.'
George R.R. Martin himself has tossed ideas out regarding a prequel series, even noting that his "Dunk and Egg" short stories would be perfect for a TV adaptation, although he also noted that would be a rather short adaptation. In the past Bloys has also stated that he was very interested in a spinoff, but it would be all about figuring out an angle a potential series could go in. Clearly, the idea has moved forward a wee bit if there are preliminary talks going on, as reported by EW, but nothing is set in stone, yet.
Of course, HBO has some time to decide whether or not a prequel is in the cards. Game of Thrones is currently filming its seventh season over at HBO, and an eighth season is still in the cards. Presuming that HBO would want to start filming a prequel or spinoff to air soon after Game of Thrones ends its run, the network would still have a year to figure out what it wants to do before the channel would even have to move forward, and that's if the network wants continuous Westeros content without a long gap, which wouldn't necessarily be the case.
One thing we do know for certain is that the current Game of Thrones showrunners won't be involved, provided HBO does decide a prequel or spinoff is the right call. Dan Weiss and David Benioff responded to questions about the spinoff a few weeks ago, noting that for them, Game of Thrones is it. The series takes a long time to come together every year and is a lot of work, and it has already made Weiss and Benioff household names. The men don't need to do Game of Thrones: The Sequel in order to keep having successful careers.