Wishbone: The problem is that you can't really make VR porn any other way than by 3D animation, which is expensive as hell. "Normal" porn made with cameras will have to stick to one of two things, stereoscopic 3D
or 6 DOF, but not both since that's impossible to do other than by 3D animation. I'm guessing it'll stick mostly to stereoscopic 3D, because 6 DOF only makes sense for porn if you place the camera in the middle of an orgy.
For a start, VR porn will be like any 360 movie, which (apart from the low res) already opens up new possibilities. I agree that it will be more interesting with multiple action scenes happening simultaneously (doesn't need to be an orgy, just more than two people), and I guess that's a direction it would take.
As for free form VR, there's technology today to convert video from multiple cameras into a 3D scene you can move through (
example: Replay). Would require more development, but I'm sure that something like this could be used effectively in porn.
timppu: Then again, maybe that would see a revival of commercial porn movies, but somehow I feel nowadays most people are so accustomed of internet being full of free porn, just like they are accustomed to cheap Steam sales or free-to-play mobile games.
It's quite common for industries to live on "whales", where the basic content is free, but if you want something better or more specific you pay, and some people are willing to pay a lot.