Actually, from the plot preview of the trailer, it looks more like Halo 2.5. Which is fine by me. There are a lot of holes about what happened on Earth while the Chief was assing around on Delta Halo and the Forerunner ship (I still want to know how Keys, Johnson, and the Arbiter got back to Earth in the first place). Why, the mere fact that New Mombassa was merely devastated and not completely wiped off the map (as it was by Halo 3) when Regret's ship jumped out on top of it is pretty intriguing. My guess would be the player character is the lucky person in the last drop pod, who wasn't
blown to pieces by the backwash from the jump.