There is a good article on FastCoLabs: What’s The Big Problem With Developing Oculus Rift VR?
It seems it is not that hard to integrate into a game. Team Fortress 2 has an Oculus Rift interface now. Valve, the owners and operators of Steam, helped create the interface.
Joe Ludwig, one of the Valve programmers behind the Rift implementation, said, “Figuring out how to combine mouse and keyboard input with head tracking was not very well explored territory, so we had to break some new ground there.”
When I was thinking about how quickly the Rift could be added to Second Life, those issues came up. What do we do with our keyboard controls and mouse? I use AWSD and the mouse in concert. I can see the Rift taking of the task of my ‘mouse steering.’ That could give me some advantage in SL combat games.
So, it seems that while integrating the Rift as a controller for a game is not overly difficult, understanding how to take advantage of the change is a problem. The possibilities for a game or virtual world change when a rift is available. The time consuming part is going to be in learning what can be done, then designing games and worlds to take advantage of that.
So, the Rift people when asked how long is integration going to take? They answer, integration is quick, but you are going to want more than simple integration and that is going to take some time.