Spoilers ahead from the Game of Thrones finale.
HBO will apparently not be showing anything that happened after Game of Thrones, but the characters' stories are continuing. Drogon was shown carrying his beloved mama's body across the Narrow Sea. He was apparently spotted flying toward Volantis. That little hint gave fans hope that the show was trying to tell us something. Perhaps Drogon was trying to bring his mother back to life.
Do you remember Kinvara? The High Priestess of the Red Temple of Volantis was introduced in Game of Thrones Season 6. She didn't need convincing that Daenerys was the one who was promised. She fully believed in Team Dany and sent her preachers to speak for Dany across Essos.
We've seen how Red priests and priestesses like Thoros and Melisandre can bring back people who have already died. So if Drogon brought Dany's body to Volantis, word would quickly spread to Kinvara. If Kinvara still believes Dany is the one who was promised, why wouldn't she bring her back to fulfill that prophecy? Also, what was the point of Kinvara's storyline otherwise?
So now fans have hope that that's exactly what happened -- and some are even pushing for HBO to air a post-credits scene:
I don't think HBO plans to do that, and it's not canon, but I do like that fan's thinking. The network seems to be standing by the story that showrunners Dan Weiss and David Benioff wanted to tell. The network doesn't even want to do spinoffs like following Arya Stark. Instead, they plan to focus on prequels and other stories in George R.R. Martin's world.
The idea that Dany and Drogon could get their own different kind of happy ending is a pretty thought:
The house with the red door in Braavos, with a lemon tree outside of her window, was one of Dany's childhood homes. It was a rare happy memory she kept returning to. If Dany was reborn, would she try to reclaim Westeros again? The Iron Throne is now gone. Maybe she'd take Jon killing her as a hint. After Jon was stabbed to death, he returned but said his watch had ended. Maybe Dany's own watch would have ended and she'd just try to find peace with Drogon.
Since Game of Thrones didn't show what happened next for Drogon, fans can continue to hope -- or just write their own fan fiction. It's possible author George R. R. Martin will write more on that topic in his final books, or the showrunners could explain their intentions with the final scene and the note that Drogon was seen heading toward Volantis.