I am not joking when I say there will be an Assassin's Creed "Primal" one day. It may even be a good game. But would it still be an Assassins Creed game? Don't you think the name should have been changed?
I don't feel the bigger arc of the Assassin's Creed games has been assassinations or the Assassin and Templar organisations. The themes of all Assassin's Creed games have remained the same: a society of freedom and chaos, versus a society of control and order. That theme is universal enough that it doesn't matter what the advocators of either are called, and the lore of the gods and artifacts means timelines don't matter either.
Of course the series has evolved far beyond what Ubisoft envisioned circa 2004-2007, when development on the first game was underway. Heck, Assassin's Creed originally came forth from prototypes under the Prince of Persia flag.