I heard on the Bungie.net forums that you have to complete the campaign on legendary with all skulls on.
Just speculation.
I also read somewhere that in one of the Halo novels, Dr.Halsey refers to a guardian and that he dies. Maybe Jun?
A campaign DLC would be cool
Hopefully we don't have to pay for it, that would make some people mad lol I personally LOVED the ending, the music, just walking around and seeing dead spartans on the ground ( appearently it's supposed to give the illusion of "Spartans never die, they're just missing in action") and that you join them after ;P
I wish we atleast saw John board the ship or something, fighting off covenant, everyone is fighting and John is just sleeping? lol
unless there's a good reason from his previous mission. I also found it corny that Dr.Hasley made Noble Six "say the words" when she gave him/her Cortana. Why him? Would she of picked Noble Six if MasterChief died? or if Noble Six survived?
I also LOVED how they sort of redid the intro to Halo 1.
plus, the AI SUCKED! I just walked through the whole thing, they couldn't drive, so I wouldnt be able to get a clear shot, and they can't shoot so I'd die almost instantly.