Assassin's Creed's lead writer Darby McDevitt has said while Altair's story arc has been finished for two years, Ezio's didn't start fleshing out until Brotherhood was in development.
Speaking in the latest issue of Xbox World Magazine, McDevitt said the only time a story is changed once mapped out is when one of the writers tosses out something cool which would sit well within the narrative.
"We have about - to give it a rough estimate - 85 percent of the Assassin's Creed lore mapped out, but new things always happen along the way," he said. "If a writer comes up with a cool new story which sits deep within the narrative, this might end up changing things. But we do have things planned out.
"Altair's complete story arc has been mapped out for two years, and Ezio's story in Revelations was being conceived and planned when the team started working on Brotherhood. So we've known the end of Ezio's story for some time - it's just a matter of working out how we present that: do we do it in a game? In a comic book? In a handheld game? In a facebook game?"
Alexandre Amancio, creative director of Revelations, said in an interview with the Guardian last week that the team made sure the game avoided “collapsing under the weight of our own mythology.”
Revelations is out on November 15.