Despite all this, the people at Collider scored something of interest. It turns out there was an alternate ending for Assassin's Creed, and it was a bit of a downer. Director Justin Kurzel and editor Christopher Tellefsen both commented on the test audience reaction to it as well as their decision-making process.
The footage in this alternate ending still has the safety wires/rigging and green screen visible, but it gives you a good idea about fate of Callum's fellow assassins. Give it a watch.