Though many see this as just another skit on Conan O' Brien's talk show, I see it as much more. The Halo franchise is proving that it is still relevant and that it can break its way into mainstream media even after years of reclusion from its main storyline.
The skit does not discuss much of Halo 4 specifically, but some time is spent at 343 Industries, where Conan does what he does best – be funny. The skits involve a voice acting booth, pitches for characters based on Conan himself, and much more.
However, the advertised "gameplay reveal" making the rounds earlier today proved to be mostly a fluke. There are indeed a few seconds of gameplay, but not what the industry was expecting. You can find the gameplay segment around 8:53 in the video, where Conan is voice acting a scene in which he is being shot via the upcoming game's multiplayer mode.
Halo 4 releases on November 6th of this year.