While I'm convinced that there are plenty of people who are unlucky enough to never be able to enjoy VR, I also think most people can "train" themselves to get better for motion sickness just by playing more
The downside is that I think I used to be more "immersed" at the beginning. Now while I do still enjoy "being" in the 3D environment, at the same time it seems I am more aware of actually being in my room (which at least protects me from motion sickness and from hitting furniture so often).