... that the letter from Ramsay was a lie meant to intimidate Jon. Ramsay learned that Mance and the wildlings had been sent by Jon to get "Arya", so he assumed that Theon and Jeyne had gone north to the Wall. He told Jon that he had defeated Stannis in order to intimdate Jon and make him give Jeyne and Theon back. Since Jeyne and Theon were with Stannis, I reasoned, if Ramsay had actually defeated Stannis he would have found them already, and wouldn't assume they were at the Wall.

But with Martin saying this takes place before the end of Dance, it makes me wonder (also, it seems possible from the description here that Ramsay might have been able to tell that Stannis had Theon and Jeyne). Could Theon have somehow been sent to the Wall with Jeyne before the battle in which Ramsay beats Stannis, and they just haven't gotten there yet by the time the raven is sent? That would set up the letter to Jon without it being a lie.

It could go either way, really. If Ramsay beat Stannis, he'll be coming for the Night's Watch next. They'll want to give him Jon and try to appease him, but the wildlings are on Jon's side, so it could lead to quite the conflict.