Unfortunately I have the be the bearer of bad news. 343 Industries did state in a bulletin following the early weeks of Halo 4’s launch answering questions, and one of them was asking if they had any plans to have Theater Mode support for Halo 4’s Campaign and/or Spartan Ops.
As of January 23rd, 2013 bs angel confirmed the bad news that at this point they have no plans to implement Theater mode support for Campaign or Spartan Ops. This does not rule it out completely, but it definitely rules it out for the time being. This is a sad day for many people who enjoy the artistic side of making machinimas or screenshots and for those who enjoy sharing those awesome moments, or moments you aren’t proud of but still can’t help sharing. I’m talking about you fails of the weak.
– Chief Landless