HBO has confirmed its future plans for Game of Thrones. The show will return for its sixth season on 24 April 2016. This will, again, consist of ten episodes.
HBO has also confirmed that it will likely renew the show for a seventh and eighth season around the time of the premiere. This news was anticipated but it will come as a relief anyway to those fearing the show wouldn't make it to the final curtain. Curiously, HBO did not confirm that these are the final two seasons, despite comments from showrunners David Benioff and D.B. Weiss that this would likely be the case. It may be that HBO are hedging their bets or considering continuing the show in a different way after the eighth season (possibly going back in time for a prequel story or adopting a more True Detective-style anthology format?).
The sixth season of Game of Thrones will, slightly confusingly, draw on storylines from the fourth novel in the series, A Feast for Crows (after the fifth season drew a lot on the fifth novel in the series, A Dance with Dragons), as well as on elements from the yet-to-be-released sixth book, The Winds of Winter.
Game of Thrones is now HBO's longest-running show currently on air and by far its most popular. HBO has been running some more experimental and drama-driven series recently, such as the David Simon mini-series Show Me a Hero and the upcoming Martin Scorsese/Mick Jagger collaboration Vinyl, but it has failed to produce another commercial hit on the scale of Thrones or the recently-concluded vampire series True Blood. HBO will be airing a series based on the movie Westworld this year, but more recently have been seen discarding promising projects (such as Dark Tower, Preacher and American Gods) that are then picked up by rivals (Sony, AMC and Starz, respectively). HBO has also optioned a TV series based on Isaac Asimov's Foundation novels, but has so far not formally greenlit it.