User blog comment:The.Outsider/AC3 Modern Day Element/@comment-58.65.148.109-20120801155618/@comment-5318922-20120804133048

I think Desmond will have some kind of eagle sense that can predict the future. When he dies, it was his prediction.

Alternatively, Desmond is an ultimate NPC in the last mission (or whatever it is called), so that he acts like how it is scripted. (But I think Ubisoft would never make him like Modern Warfare's Captain Price)

Or maybe you want to look back at the Desmond's (pretty short) gameplay at Assassin's Creed II and Assassin's Creed: Brotherhood