http://www.ew.com/article/2015/03/11/game-thrones-end

"We'll have an honest conversation that explores all possible avenues," says HBO programming president Michael Lombardo. "If they weren't comfortable going beyond seven seasons, I trust them implicitly and trust that's the right decision—as horrifying as that is to me. What I'm not going to do is have a show continue past where the creators believe where they feel they've finished with the story."