[Note: This article reports on Martin's trip to Slovenia, and is in Slovenian. However, the embedded video features Martin discussing the genesis of the novels and shows other details from his trip.]
[Note: This report is somewhat garbled, but we'll leave the text as is. In fact, it's not the title of the story -- it is, instead, the title of the anthology that the novella will appear in, the title giving away the theme of the anthology... and so still supporting the idea that it likely involves the Wolf Women of Winterfell.]
"Dangerous Women".
That's the title for the planned fourth Dunk&Egg novella. George said as much Friday last week in Poland. I was there. Unfortunately the other answers to questions are not that revealing.