Originally posted by KeggeWell, that's up to the director of said movie, really. If he's someone like J.J. Abrams, he'll just throw out canon and make it about whatever the hell he wants.
But they aren't! The second movie isn't directly based on the sequels by Jeter ... or do you have a confirmation somewhere that they are.
Now ... on which book is the sixth season of game of Thrones based? On which book is the second season of The Leftovers based?
The sixth season of Game of Thrones is based on The Winds of Winter, which hasn't been released yet. Since George R. R. Martin is working closely with the series, the season can easily follow the yet-to-be-released book.
I have no clue about The Leftovers.