Every Game Of Thrones Spin-Off Currently In Development
5. An Animated Drama
This is currently the potential series with the fewest known details. Reportedly this will be an 'adult-leaning' project, that will still capture the tone of Game of Thrones completely. With much of the fantastical side of the World of Ice and Fire as of yet unexplored on screen, animation rather than live action could open a lot of doors without the constraints of CGI budgets.
If reports are to be believed, HBO is working towards this series being a exclusive to HBO, though this is all that is known about it right now.
There are no details as to the story, where, or even when it will be set in George R. R. Martin's world, but given that the majority of these series are set to be based largely in Westeros, it would be interesting to see this take place across the Narrow Sea in the Free Cities, or even further afield in the shadow lands of Asshai or Yi Ti.
Another interesting concept that could be explored would be to answer the question Arya asked in the finale of season eight, when she teased the mystery of what lies west of Westeros. This wouldn't need to feature the Stark girl at all, but could still dig deeper into this side of the world.