one century, 100 years?
possibilities:
1) the guy lived an extra ordinarily long life (living to 100 is nothing new but he started something 100 years ago. so he must be even older)
2) there is a mistake and he should have said half a century or something
3) technology allowed him to live longer (nano machines improve body or what ever, similar to nano machines in crysis 1 that helped in speed mode (see old crysis 1 trailers if you don't know about these))
4) i have bad ears
It is obvious of course Crysis 2 takes place a century later after the the Original Crysis. SO there for the narrator in the trailer is more than likely Nomad.
The Nanosuit must have had some sort of aging affect on the human body / DNA