I think I found out how the White Walkers are going to get past the Wall. In the Season 7 opening credits, we got a clue when we saw the Wall. If you look closely, you will see that the ocean on the eastern side of the Wall is completely frozen. Due to this, the White Walkers are not going to attack the Wall directly. Instead they are just going to go around it by crossing the frozen ocean on the eastern side of the Wall. This is similar to what happened in 1940 with the Maginot Line, which was designed to halt the Nazi’s military offensive in France. However, even though the Maginot Line was impregnable, the Nazis simply went around it, which led to the evacuation of Dunkirk. I think the White Walkers are going to take a similar approach with the Wall. This might be one of the reasons why the White Walkers waited until now to reveal themselves. They were not just biding their time to rebuild their strength. They were waiting for a winter that was cold enough to freeze the sea on the east side of the Wall so they can go around it. If the Night’s Watch finds this out, they will be so cross that they defended the Wall ultimately for nothing.