Burning shafts hissed upward, trailing tongues of fire. Scarecrow brothers tumbled down, black cloaks ablaze. "Snow," an eagle cried, as foemen scuttled up the ice like spiders. Jon was armored in black ice, but his blade burned red in his fist. As the dead men reached the top of the Wall he sent them down to die again. He slew a greybeard and a beardless boy, a giant, a gaunt man with filed teeth, a girl with thick red hair. Too late he recognized Ygritte. She was gone as quick as she’d appeared.
It's often hard to know whether these dreams of Jon's actually foretell anything. The eagle must refer to Orell, the skinchanger that lived on in his eagle before Melisandre killed him. The rush of people climbing the Wall like spiders reminds one of the spiders that the Others allegedly rode as mounts during the Long Night. The one thing that draws our attention to this as being potentially prophetic, however, is his sword "burning red". This sounds very much like the description of the Red Sword of Heroes which belonged to Azor Ahai, and which Azor Ahai reborn is supposed to carry. For various reasons, A Dance with Dragons has reinvigorated speculation that Jon Snow is Azor Ahai reborn.