It's difficult enough to make a perfect TV show, but it's even harder to do it twice in a row. But that's what happened with Avatar: The Last Airbender and its sequel series, The Legend of Korra, which takes place one generation into the original story's future. By comparison, Game of Thrones (another epic world-spanning series) was far from perfect, but if HBO wants fans to return for a GoT spinoff, it needs to steal a few ideas from Avatar.
Before you even mention it, yes, I know the only official spinoff so far is a prequel series set long before the events of Game of Thrones. But we also know that HBO is working on multiple shows in this universe, and The Legend of Korra proves pretty conclusively that it's more than possible to do a sequel series that pays tribute to the original while taking the story in bold new directions.
For those unfamiliar, Avatar takes place in a fictional fantasy world divided into four groups (the Fire Nation, the Earth Kingdom, the Water Tribes, and the Air Nomads). Select people from each group can "bend" their respective element, essentially giving them superpowers, and the Avatar can bend all four, giving them the power to balance the world. The Last Airbender follows Avatar Aang as he and a group of friends and allies take on the fearsome Fire Nation. The Legend of Korra picks up 70 years later with the next Avatar (it's a reincarnation thing) as Korra faces new challenges in a rapidly modernizing world.
Familiar faces — By shifting its story a generation ahead, The Legend of Korra was able to explore what happens after The Last Airbender while also introducing a new cast of characters. We get Korra, Asami, Mako, Bolin, and some stellar new villains, but we also get to meet Aang's son Tenzin (voiced by J.K. Simmons!) along with the all-grown-up versions of familiar Last Airbender characters like Zuko, Toph, and Katara.
The Legend of Korra didn't spend that much time with those old favorites, but when it did, fans loved it.
Setting a Game of Thrones spinoff decades after the series finale would allow HBO to try something similar. We could get a fresh story in Westeros, while at the same time offering a glimpse at what lies in store for Arya Stark, Jon Snow, Tyrion Lannister, and others.
The story continues — More important than these individual characters, The Legend of Korra explored the geopolitical fallout of The Last Airbender. The story begins in Republic City, the capital of the United Republic of Nations founded by Aang in the gap between the two shows. But this new peace quickly reveals multiple fractures, from an anti-bending cult leader named Amon in Season 1 to an Earth Kingdom nationalist determined to reclaim the territory her people seeded to create the new republic.
Considering the tenuous political state of the Six Kingdoms (plus the North) at the end of Game of Thrones, it's silly to think that nothing bad will ever happen again. That said, most fans aren't particularly interested in the day-to-day realities of King Bran the Broken's rule. By jumping decades ahead, a Game of Thrones spinoff could reveal the long-term ramifications of Bran's leadership while also exploring what a slightly more modern version of Westeros might look like.
I'm not saying we need steampunk zeppelins in King's Landing, but the people of Westeros have got to be due for some sort of industrial revolution.
The risks of a sequel series — Of course, there are plenty of drawbacks to revealing what comes after the finale. For one thing, it robs the audience of their own imagination. Right now, you can believe whatever you want about the future of Westeros, but once a sequel exists, it becomes the only legitimate answer to what happens after the finale.
That can be a good thing (like with Korra) but it can also end poorly. Consider the Star Wars sequel trilogy, which had plenty of good ideas but ultimately ended in disappointment. By focusing too much on fan service and not enough on actual storytelling, Star Wars cheapened not only the new movies but the entire franchise.
In other words: As long as a Game of Thrones sequel doesn't bring the Night King back and pretend like he never died, it should be okay. Korra might have featured some Last Airbender characters, but the villains were always fresh and original.
Star Wars aside, the Avatar franchise offers a clear template for taking a show people loved and making even more of it. HBO's current plans might not include a sequel like The Legend of Korra (at least not officially) but if the network has any brains at all, it should seriously consider the idea.