Was thinking again for some reason on the trailer when I yet again came up with something.

In the trailer we all know that the armor was different, new. I was thinking at the start of Halo 2 you where given new armor. Well the gap of the game in Halo 2 was only a day or so, not enough time for a new set of armor to be made when under an invasion especially.

This means that the Spartan in the E3 or Announcment trailer (which ever you take it as) could only be a different Spartan, which would also be a good reason on why the character didn't speak.

I'll try posting it on Bungie to see if I can get anything.