So there’s one Multiplayer map yet to be revealed for release, and it was sighted in the Making Infinity Multiplayer video. I believe it’s called Vortex, and though it looks large, it looks too cramped to hold a Mammoth.
So it seems like we won’t get a Multiplayer map at release that is big enough to hold a Mammoth.
However, today, all nine multiplayer DLC maps, to be released December, February, and April, were announced, and even some concept art was shown.
http://www.examiner.com/slideshow/halo-4-map-pack-artwork#slide=54498351
I don’t think it’s likely we will never get a map with the Mammoth on it in Halo 4, and I actually think it makes sense for 343 to wait until DLC to offer a map with it. It would really help the DLC sell. Bungie did something similar by not releasing Foundry, the first Forge map, until the Heroic Map Pack came out.
Which of the DLC maps, shown in the concept art, seems like it could hold a Mammoth? My guesses are Harvest, Daybreak, and Outcast.
Harvest, I think, is the most likely of all, because it is in the Crimson Map Pack, the first wave, and looks massive, whether or not the background of the concept art is part of the map. We’ve seen lots of shots of the Mammoth in an arid place, and Harvest (an agricultural planet) would be a perfect place for it stylistically.
Thoughts?