Of the many Game of Thrones spinoffs being planned, the upcoming Jon Snow show is said to be the most ambitious and interesting, as it actually continues the character's story after the end of Game of Thrones - and Kit Harrington is also on board.
However, in an interview with Deadline HBO's head of drama Francesca Orsi says that it is not certain that this series will happen in the end:
"We're just working deeply with the writers to get it in shape for potential greenlight, but at this point, no, no determination on whether it can go all the way."
This is the only one of the revealed spinoffs that moves the story forward, while the rest are prequels, like House of the Dragon.