Then today I saw one of the Trophies/Achievements for HH was "Evacuated Zion" and I put that together with the leaked images from the trailer. Specifically that it looks an awful lot like the Grand Canyon. Obviously the Van Buren information on Wikia isn't necessarily what we will see in the DLC, but my brain put the above together and made me think of this bit from it;
http://fallout.wikia.com/wiki/Ballistic_Orbital_Missile_Base_001
"B.O.M.B.-002 did not fare as well. Sometime during the two-hundred years of silent orbit, perhaps ten to fifty years before 2253, something big hit B.O.M.B.-002 and sent it crashing down to earth. Pieces can be found in the Grand Canyon, but how big the pieces are, and if there is anything salvageable, remains to be seen."
Could we be dealing with the tribal people (Sorrows?) inhabiting the remains of the fallen B.O.M.B - 002 and the Burned mans attempt (supported by the opposing White Legs) to acquire the Nuclear devices it had on board? Perhaps with the intention of taking out Caesar/NCR whoever he feels has wronged him?
I can see it being in our best interests to crush this possibility before it becomes reality, as the alternative would be fighting off nukes with my Plasma Rifle?
I'm thinking it may play out that we're going to have to foil his plans by seeking out the launch/activation codes, detonating them but bugging out the Sorrows before hand/or not (Evacuated Zion).
Just a thought, but thought it might be worth sharing.
You might have hit the nail on the head there, why else would we evacuate Zion? Man I hope we can help him in his revenge scheme, it's what I would do first anyway, the burned man has always been a character I've been interested in.