Ugh. This guy's an idiot. Yes, the Cheif is awesome. Yes, I got more giddy than worried when I saw the Halo 4 teaser. But he is NOT the only thing in the Halo universe. And being about as close to a fanboy without being unsufferable (hopefully) as I am, I probably would have been much more ape-shit if I was shown a teaser of a game focused on post-war Humans and Elites. In fact, I think post-war Elite society is one of the most interesting stories available to tell! (If you have Halo Waypoint, watch "The Return" to see what I mean.)
Other things I would have been more excited to see in a game than MC: Forerunner-Flood War, the Covenant prior to first contact with humanity, a child-adult protagonist undergoing Spartan training. The list goes on.
Hell, you could even cast the Cheif as the main character in that last one. That might even add depth to the other games. When I play Halo 1-3, I'm thinking of him as that archetypical stoic cowboy, whereas a real man-of-few-words, having been through what he's been through since age six, is more likely repressed and unhealthily detached emotionally from reality. Actually, I hope the "personality change" announced for the Cheif deals with him snapping under, or at least coming to terms with, all the bullshit that had been laid on his shoulders since childhood. Actually give some depth to his in-game character (haven't read any of the books, but I hear he's more interesting in them).
For now, I'll trust 343 Studios not to rape the IP, since all the guys and gals running it were hand-picked by Bungie, but Microsoft should neither be so heavy-handed in directing the studio nor force the series to stagnate. There are too many facinating places for 343 to go with this universe to focus exclusively on one character.