A few months ago the Game of Thrones saga came to an end with its final eighth season. Now GoT creator George R. R. Martin comments on the future of the franchise in form of a spinoff about the Targaryens. In contrast to the other unnamed prequel, whose first episodes have already been filmed, the planning for the Targaryen spinoff is still in its beginning. On Martin's website Not A Blog he not only announces his thoughts on the upcoming series, but also confirms the work on it with the following statement:
The pilot on that one wrapped a month ago and has been in post-production.The show stirring up all the internet headlines right now is one of the others. Also a prequel. Set
thousands of years after Jane’s show in the history of Westeros. And yes, it is based on material from one of my books.
The book mentioned is, of course, Fire and Blood, which story takes place about 300 years before the events in GoT. Martin also adds that this book offers a base for dozens of series. However, the production hasn't moved much forward yet, as at the moment only the script for the pilot episode is roughly finished.
The author, who turned 71 a few days ago, raises hope for fans who are looking for more GoT spinoffs, as he has plans to produce more spinoffs.
Unfortunately there is currently no release date for either of the two spinoffs.