Anecdotal, but a lot of people seem to be able to get over their VR motion sickness. I personally did by just playing the janky Rocket Mode in Richie's Plank Experience a lot. Same goes for heights in VR, at first it's terrifying but if you repeatedly expose yourself to it it loses its effect. There's also a story of a VR dev who built a demo to get rid of his motion sickness, it involved just repeatedly dropping his POV from a height and then looping back to the top. Granted, some people will probably never get rid of their motion sickness for whatever reason but I think those will be in the small minority.
To me it sounds similar to all the reports of motion sickness (or worse effects) from playing Doom back in the day. I also suspect most people who do suffer from it can get used to it over time.
OTOH, considering how many people keep having motion sickness in cars (especially when not driving and reading and whatnot), perhaps for some people the issues remain.
