Well, it's certainly the most convincing one I've seen. One thing that bothers me is the weapon info in the top right corner. After Halo 3, weapons are shown with the barrel facing left, but the DMR (I presume) is inverted. It doesn't really prove anything, but it's weird.
The dmr looks like it's The same model as the one posted in a previous topic.
This one? http://www.gamefaqs.com/boards/632877-halo-4/61741914