While one Game of Thrones spinoff may have been cancelled, HBO is pushing forward with the Targaryen-focused House of the Dragon. While we don't have a main plot for the series yet, the show has cast one of its first key roles.
According to Variety, Paddy Considine (The Outsider) has been cast as King Viserys Targaryen I. Here's his character description:
Considine has signed on to star in the series in the role of King Viserys I, who chosen by the lords of Westeros to succeed the Old King, Jaehaerys Targaryen, at the Great Council at Harrenhal. A warm, kind, and decent man, Viserys only wishes to carry forward his grandfather's legacy. But good men do not necessarily make for great kings.
That final description really kind of gives off the vibe that Viserys is going to be the "Ned Stark" of this series. While honorable and good characters make for great heroes in fairy tales, they have no place in something as lawless as Game of Thrones.
If you did your lore research, you'll know that Viserys is the father of Rhaenyra and Aegon II Targaryen—two central figures in the Targaryen Civil War that has been called The Dance of Dragons. While I suspect that those two characters will be the main protagonist/antagonist, I'm kind of hoping that we also get to see what the Starks and Lannisters are up to at this point in time.
No release date has been set for House of the Dragon, but the show is expected to come out sometime in 2022.