There is this Easter egg in the mission with cayde - 6 stash, where you find a card. He says one of the three cards represents a girl (queen of hearts) , my theory is that it is the stranger, only because in the collectors edition of The Taken King, you get a journal where he talks about an exo female doctor... I'm thinking the two are tied together, not to mention that when you enter the room it talks about "his exotics" and that they're missing... HMMMN