This reportedly was confirmed by HBO’s president of programming Casey Bloys, who wouldn’t offer any more details, however, he noted that the writing for the series is underway and that there are no casting details to announce yet.

“There are no other blinking green lights or anything like that,” Bloys told Deadline. “Sometime down the road who knows, but there are no immediate plans. We are all focusing on House of the Dragon.”

Per the outlet:

House of the Dragon is based on George R.R. Martin’s 2019 book Fire and Blood. The book is set 300 years before the events of Game of Thrones and relates the history of the Targaryens, beginning with Aegon the Conqueror’s initial conquest of Westeros and his bringing the Seven Kingdoms under his rule.

The book then jumps through the decades, touching on each successive Targaryen ruler and the politics, civil wars, and intrigue throughout history. (So far, Martin has just published the first of two planned Fire and Blood books, covering the first half of the Targaryen dynasty. A second book that will cover the remainder of the family’s history up until where A Song of Ice and Fire starts is planned for the future.)

Source:https://www.hollywoodreporter.com/