There is a long fan theory predicting Arya will be the one to take down the Night King — and it's pretty convincing. Remember when the Faceless Man fell dead and Arya took off his faces until she came upon her own? Well, that's a sign that Arya has lived, died, and lived again. Let redditor XHelheimX explain: 

"The Faceless Men can only have faces of people who have died. There are no replicas. As a true Were, Arya is able to easily master the magic of skinwalking and to see her own face only means one thing. She has lived and died before," they wrote. "Arya is given an ancient Valerian Steel dagger by Bran. As he hands it to her he looks worried and sad. Bran already knows what his sisters fate is. As the Crone he is the seer of man’s fate. He knows that Arya is death and to end all the dead and make sure they are returned back to the other side, Arya must fully embrace her nature. She is death." 

The theory ended with, "Now I’m not entirely sure how the show will wrap up. However, it seems to me that the only thing that will stop the dead is to make sure the master of Death is back in the realm of the dead. Arya will be the Queen of Death. For this to happen she will die."