For a time in January 2017, Season 8 renewal was put on indefinite hold, due to a disagreement between HBO and the showrunners over the number of episodes it would contain. While originally Benioff and Weiss stated they intended 7 episodes for Season 7 and 6 for Season 8, apparently there was some internal pushback that they should make more than six episodes (whether for story reasons or purely business/budget reasons is unclear).
[3] At their SXSW panel on March 12, 2017, Benioff and Weiss announced that Season 8 will consist of the originally planned six episodes. No new writers will be introduced: Dave Hill will write the first episode, Bryan Cogman the second episode, then Benioff and Weiss will divide up the remaining four.
George R.R. Martin will not be returning to script another episode.
The final season could contain multiple episodes of up to two hours long in length and could be the longest season to date, even though the season only contains 6 episodes.