I was just reading into the history of the real Masyaf, and apparently, in 1260, it was attacked by the Mongols. Well, that would make Altaïr 95, and in the secret crusade book, he will be 92. I'm thinking we may finally find out when Altaïr dies. He lived to be very old, after all. I'd say he's lucky to have made it past 50 back then. Or, alternatively, Altaïr is helped later that year to reclaim Masyaf, as that happened in real life as well.
Let's just go ahead and hope we finally find out what happened after the events of Bloodlines, the writing of the Codex, and Altaïr heading to Mongolia.