Someone somewhere said that the real problem with a time skip in hindsight would be that the new status quo Martin was setting up, while an excellent starting point, was both a) a bit too complicated, and b) had far too many interesting things happening to far too many characters the audience was already invested in.
It's one thing to be introduced to a character who's famed in legend when we meet him, then get to know him. It's another thing entirely to get to know a character, enjoy them, then come back and find that you missed out on some totally awesome **** between books.
In other words, Martin wanted to "reset the game board" but the new set up was far too epic to be skipped over. The issue is that to set it up, Martin had to let characters stew around each other and go off on quests to burn time while BIG things were happening, but not at the pace of the first three books. And like any author of a successful series, at a certain point while writing, he was inspired to expand other parts of the world and cast, and no editor would tell him "No."
Anyways, do you guys think the Wildling fort in the trailer is part of Hardhome? Or is that a different setting?