EW and Variety are both reporting that the tentative plans for Game of Thrones is for it to run 73 episodes, which would mean a shortened 7th and 8th season (as opposed to the earlier, original plan of 7 10-episode seasons). Nothing is set in stone here, but Dan Weiss and David Benioff had previously shared their plans with EW, saying they wanted to wrap up after episode 73, which would mean a 7-episode seventh season and a 6-episode eighth season.
This, of course, can change. The final two seasons have not officially been announced, and undoubtedly, HBO will push for more (in fact, HBO has since released a statement saying that any talk about the future of the series is speculative and that these decisions will ultimately be made by the network in consultation with Weiss and Benioff).
This announcement comes at a precarious time for the network. It’s struggling in the drama department, and nothing on its schedule approaches the ratings of Game of Thrones. The Leftovers is ending after season three. True Detective slumped in its second season (and a third still hasn’t been announced). Westworld has been delayed several times, and the show it had pinned its future on, Vinyl, has performed so badly that the showrunner, Terrence Winter, was fired.
HBO obviously wants to milk the series for as long as they can, but I think they’ll ultimately respect the wishes of Weiss and Benioff, who obviously want to finish the series themselves and on their own terms under the outline they have planned.