The War Of The Three Queens Is Coming So Which Three Queens Was Littlefinger Talking About?

At the end of A Feast For Crows Littlefinger tells Sansa "What little peace and order the five kings left us will not long survive the three queens, I fear." And Sansa doesn't know what he is talking about. I have seen discussions over the years about which three queens he means and I think I finally have an answer I am fairly confident in. So I wanted to break down the different options and arguments for them, then go by process of elimination until we find the most likely answer. So who will take part in the war of the three queens in the winds of winter? Let me know if you agree with my conclusion.