Yeah, that seems to be a problem. My plan is to create a separate non-VR scene in Unity, where I have full control of camera movement, and then run that scene at 60 Hz. But as I said, that is only a plan at this point, as I am still not at the stage in my game development where I could get good enough footage for my trailer. If someone has better ideas, speak up!
Working on LineWars VR: http://linewars.patrickaalto.com/LWVR.html
Dumb idea (and not even looking at the Rift myself): can you record at the full frame rate and reduce the frame rate in your video editor (at the very least this should be able to blend frames rather then dropping them, but good video editors can probably do more intellient interpolation)