During an interview with 343 Industries' Halo director Frank O'Connor told CVG that Master Chief will have."some fairly radical modifications to his armour." He also went on to say that some of it will be artistic changes and some of the armour changes are due to the fact that Master Chief has been out in space for a while.
O'Connor went onto say that Master Chief wouldn't be the only one getting upgrades. Because her life span, Cortana was only supposed to last seven years. Adding she how taken in more information then any other AI ever made and which may cause some issues in Halo 4 and beyond.
Personally, I don't give a shit what Master Chief looks like just as long as it's nothing like the characters everyone has been seeing in those Saints Row: The Third commercials. I can't wait to be blasting little grunts and bitch smacking some fucking brutes!