Ok, I know it might be far-fetched but I was wondering if it was related with the AA prophecy. We know that in order to create the Lightbringer, Azor Ahai sacrificed Nissa Nissa. If we assume that Jon is AA reborn, his Nissa Nissa would be Arya, since she's the person that he loves the most.
Also, in the chapters of GOT when Arya is having her water dancing lessons with Syrio, he says to her "Boy, girl, You are a sword, that is all.".
What if "Kill the boy and let the man be born" is not just a saying about Jon being mature, but it also foreshadows future events from TWOW?
Thoughts about that?
**In my opinion, Arya is more qualified than Ygritte to be his Nissa Nissa, if Jon is indeed AA. Jon indeed, loved Ygritte, but for Arya he was ready to break his vows to the Night's Watch, before ending up getting stabbed.