Never even noticed, I'm blind as a bat lol
Its doubtful to be a video after effect. Putting code into the game engine even for just this video is far easier than adding the effect after the clip is recorded, and more accurate at that. Putting a blur in video clips for a trailer or even videos like this has never been done in halo before unless its a major trailer that might be seen on TV or a big announcement video. To write the code into the game just for a minor video is more work than is necessary, even for just a cool effect. Franky has stated in Q&A's that they want to innovate in many areas and one being Theater mode. While i still don't know if its possible that they can update this to all of theater mode and not just these three maps which would make it useless, the probability is good. And i can tell by close examination that the blurred scenes are coded because of the fluidity and quality of every object being blurred in the scene. Also a lot of end scenes use distance blur and it makes no sense to do this because it blurs the very thing they want to show off, the maps. The put heavy emphisis on blurring where blurring wouldn't be needed
After all it would be a big quantum leap in video capture for almost every player from Machinima makers to strait up screenshots and funny clips. And would put Reach's video system ahead of all competition.
I would say its hopeful, but your right that we cant hold our breath.