Although the focus of the series is going to be the Age of Heroes, there's a suggestion that we'll see at least some of the time before that. After all, the Age of Heroes didn't just materialise out of nowhere, but instead came after years of warfare between the Children of the Forest and the First Men.
That eventually came to an end with the signing of the Pact on the Isle of Faces, which gave the men rule over open lands while the children kept the forest areas.
Game of Thrones had a cold open of the White Walkers in its first ever episode, and this could offer up a similarly memorable prologue to the new series: the two races coming together in a unique location (a small island in the middle of a lake in the Riverlands) to sign a treaty and usher in a new age, before launching into the show proper.
It's still one of the most important events in Westeros history, helping to shape the next few thousand years of the continent, and there's a real chance to show it here.