If there is one thing I can say about Halo 4 is that I love the design of the new sangheili's body. A more vicious version of the Halo 3 style. Make them have emotion with colored irises (Halo Reach's pure black was nice but not truly them.) But have their teeth sharp and jagged but also include molars so they actually can chew food. Their eyes also face forward so they aren't like an animal and can see their foes/prey.
Since the Halo 4 will never have a theater mode for campaign or spartan ops I'm left with pausing the game mid fighting to try and guess how their head is shaped. (Although I'm waiting for their model to be appear in either XNALARA or garry's mod so I can get it truly right.)