I'm a GoT homer so my take migth be a bit over the top, but...
Without Jon, the army of the dead would have had every single Wildling, the northern houses aren't united, the Boltons still hold Winterfell (with a lil help from Sansa), Dany doesn't bring her Dragons, Dothraki, and Unsullied to protect the North. He's never been an elite warrior/killer and he hates ruling. Not to mention, Arya, the killer of the NK, doesn't even go to Winterfell if she didn't hear that Jon won the Battle of the Bastards.
Don't think his arc is defined by not killing the NK, and we still got 4 hours of episodes left.
Side note, how mad is everyone gonna be when there isn't another big battle? I'm expecting some treachery similar to the Red Wedding rather than a big battle, either by Euron or Tyrion.
Yara is gonna show up with Daario Naharis and a bunch of ships full of sellswords and former slaves to help turn the tide of battle outside the city walls and on the Blackwater... Cersei's forces and the Golden Company will be dispatched without much fanfare.
The drama will happen when Cersei refuses to give up the Throne or open the gates of the city, and threatens to burn thousands of innocents with wildfire.
The penultimate episode (or the early part of the finale) will turn into an intense rescue mission, where Dany instructs her forces to save as many people as possible, while a select crew of heroes (Jon, Clegane, Arya, Jaime, Brienne) brave the green flames and chaos to storm the Red Keep and face down the Kingsguard and the Mountain.
Brienne, Arya and Clegane all die in order to take out the Mountain.
Jaime is fighting Euron, and about to strike a killing blow, but Cersei SHOOTS AND KILLS HIM with the crossbow she gave Bronn, which he leaves behind when he goes to find and save Tyrion amidst the chaos.
As Jaime and Euron both die, and Jon confronts Cersei, Sansa calmly walks straight for the throne as the world burns around her, and sticks Cersei with the pointy end... Sansa is ALSO a volanqar to Cersei, and the prophecy will be fulfilled.
Sansa tells Jon that the throne is his, while Rhaegal crashes in through the roof of the throne room to rescue them both before the fire claims them.
