The time has come to consider possible Game of Thrones Sequels. Here are some suggestions that will surely make GOT great again!
The Great Dothraki Rebellion. The new king and his council have time to consider such important issues as reopening the brothels of King's Landing. But they appear to have forgotten that there is still a large Dothraki horde in Westeros. No one has made any effort to resettle them, or even to try to keep them from getting angry and revolting. Yes, I know it seemed like nearly all the Dothraki were killed in the Battle of Winterfell. But this is contradicted by Episodes 5 and 6, where we see Dothraki troops in numbers comparable to what they had in pre-Winterfell battles. Frustrated by the new government's neglect, the Dothraki revolt!
Daario the Conqueror. Daario Naaharis unites Essos under his rule and invades Westeros to avenge the death of the woman he loves.
For extra fun, a combination of 1 and 2. Perhaps Daario makes an alliance with the Dothraki.
The Wealth of Westeros. The Iron Bank of Braavos demands repayment of the large debt incurred by Cersei's regime. They refuse to accept the excuse that Cersei was not really the legitimate queen, and therefore had no right to draw on the public purse. If the new government defaults, Westeros' credit rating will go in the toilet. They must either raise taxes on an already impoverished population, massively increase economic growth, or some combination of both. George R.R. Martin famously criticised Tolkien for not telling us enough about Aragorn's tax policy after the defeat of Sauron. This scenario is an opportunity to make sure Martin's own fictional world avoids the same mistake!
The Great Winter Famine. Another issue the new government seems to be neglecting is the threat of famine! Winter is STILL Coming, and most of the harvest from Westeros' biggest food-producing region got plundered by the Lannisters and then burned to a crisp by Daenerys and Drogon in the Loot Train Attack in Season 7. This is an obvious scenario for famine. Is the new regime up to the challenge? I wouldn't bet on it! If not, there could easily be more war and rebellion.
Arya the Explorer. Arya sails West and finds Numenor! Or maybe she encounters the Dawn Treader.
The Return of the Dragon. Drogon comes back and decides that humans have made such a mess of things that Westeros will be better off if ruled by dragons. Perhaps he has given birth to some new baby dragons through asexual reproduction in the meantime (it is still unclear exactly how dragons reproduce).
Horror Beyond the Wall. Jon Snow and Tormund settle down to what they think will be a quiet life in the far North - only to discover that more undead lurk there..... this time led by a Zombie King who is actually smart.