Mainstream VR? Fuggedaboutit...
...certainly in 2016. I suspect that IF it becomes 'mainstream' in the niche that is hardcore gamers (and that in itself is a big if) then it may eventually trickle down into the wider gaming community.
Getting from there to standard consumer product? Well, how many people do you know who regularly use those 3D glasses that came with their 3D TV?
I think that solving motion sickness is the least of their worries.