Jon stabbing Dany would fufill the AA prophecy. Jon is stabbed and his body is burnt on a pyre (not sure where the salt comes into play but theres your smoke). Jon gets revived on the pyre in the Melli Mel ritual. Maester Aemon will spill the beans to everyone about Jon on his death bed. Jon rallies enough support against the White Walkers and defeats them. Dany gets to Westeros too late and nobody respects her claim. Furious that her entire life's dedication goes unrealized, she goes full Mad King and wages war against Jon. Jon defeats her in battle, stabs her in the chest, and her soul binds to Longclaw. Lightbringer byke, Jon is Azor Ahai.
In the prophecy, Azor Ahai has to kill his wife to forge Lightbringer. Since Longclaw was intended to be Jorah's sword before his exile, and its used to kill Dany (the love of HIS life), its not unreasonable to believe that this becomes Lightbringer.
Also, this is why Maester Aemon seems to know who Jon is on the show, and why Ned would send Jon to the Wall knowing the time would come when Jon would need to know the truth.