the teaser for Halo 4, our first question was: "What is up with that armor?" Last time we checked, he didn't have a jetpack. Could Master Chief actually be Barry Steakfries?
Nope, it's all part of 343 Industries' plan to update the Master Chief's armor for Halo 4. A blog post on Halo Waypoint discusses the "800 pounds of tank and jet fighter" strapped to Chief's frame. "So we pulled that design into the armor and HUD. When you play Halo 4, it's important you understand that you're more than just a gun on the screen. To give you that feeling, we have represented that weight with player physics, without interrupting crosshair and shooting accuracy."
Despite Chief's bulk, 343 describes him in Halo 4 as "a nimble yet heavy superhero." His design will contrast against the bulky Spartan armor design seen in Bungie's last effort, Halo: Reach. "When we first looked at the Chief's armor, we studied what was done in Reach. We knew he needed to be understood as a nimble yet heavy superhero, and contrast that with Reach armor design that was more on the bulky side. Our goal is to hit that sweet spot where we represent what is fictionally true about the Chief while making sure you feel like you're a super-powerful human being when you're playing him."
In short, 343 is aiming to better convey his physical weight to the players -- and it sounds like his movement and characteristics will reflect that. Whether it'll come with a more complex, busier HUD remains to be seen.