Nausea in VR is already a solved problem, at least for the case where you have a stationary camera. This is for giving people an extra method of depth perception, but one which isn't strictly necessary.
I say this as a VR enthusiast who is optimistic about the industry.
You can't say it's solved until an HMD can forcefully move your viewport in-HMD without triggering nausea caused by the real body not moving.