I think Jon had to die so he could infiltrate the Other's camp as an undead. I think he will use one of the three bodies he dragged in from the woods and warg into one of them. It was some reason those three bodies didn't turn to undead... Jon will do the Others like he did the Wildlings. He will blend into their camps and figure out how to stop them. That is the only way I see the NW stopping the Others. We know the wall will not fall. Jon set to many wheels in motion to allow that to happen like setting up loans with the Iron Bank. Then he is making the NW for the first time self sufficient. With the wildling, the NW will have new recruits on a normal basis and truly become independent. I believe in the end the NW will hold the wall and save the world and no one will know who saved their butts. The murders, rapist, and thieves will end up saving everyone and no songs will be written about them. That just seem very GRRM...