You are wrong. I have dreamed of your Wall, Jon Snow. Great was the lore that raised it, and great the spells locked beneath its ice. We walk beneath one of the hinges of the world." Melisandre gazed up at it, her breath a warm moist cloud in the air. "This is my place as it is yours, and soon enough you may have grave need of me. Do not refuse my friendship, Jon. I have seen you in the storm, hard- pressed, with enemies on every side. You have so many enemies. Shall I tell you their names?"
"It is not the foes who curse you to your face that you must fear, but those who smile when you are looking and sharpen their knives when you turn your back. You would do well to keep your wolf close beside you. Ice, I see, and daggers in the dark. Blood frozen red and hard, and naked steel.
The final Jon chapter should make everything quite clear. The smiling faces sharpening their knives are the men of the Night's Watch, led by Bowen Marsh, who attack Jon Snow following his declaring his intent to ride south to deal with Ramsay Bolton.
Although not a prophecy, Melisandre's declaration that the Wall is one of the hinges of the world bears a look. As she notes in her own chapter, her power is greater at the Wall than anywhere else she has been, even Asshai. It's clear that there is potent magic in that area, perhaps in part due to the fact that the Wall itself is partially built of magic (though this is not really known except to a very few). GRRM's non-canonical story for the Suvudu cage match put forward the notion that there are places in the world where magic runs deep, but they are very few, and most places have very little magic in them; could that be a reflection of the actual metaphysics of magic in Westeros? The Wall is one of those places, however. We wonder if the potency of magic there isn't just because of the Wall, however.
Can it relate to the weirwood grove not far away, or something else connected to blood? To go out on a limb, we wonder if it's not possible that the power of the Wall is not in part due to a great deal of human sacrifice to ensure its lasting power...