As a car enthusiast, I can think of a good one, the Ford Nucleon.
During the 1950s and 1960s, there was considerable interest in nuclear power and its potential applications. This led to the idea of using nuclear energy to propel cars. The concept behind a nuclear car was to utilize a small nuclear reactor to generate steam, which would then power the vehicle's engine.
Of course back in those days, this was extremely futurustic and some at the time thought this would be a game changer, but ultimately, the safety aspect was one of the biggest reasons why this idea was dropped, and I probably don't have to explain why it may not have considered to be safe, I mean, it was using nuclear power, so even if the engineers tried to make it as safe as possible, IF something went wrong, it would have been catastrophic.
Ever since then, the interests in the automotive sector has shifted to Electric and Hydrogen.
Still, a very intriguing concept car and idea.
Outside cars, you have blimps, and I personally believe if we tried to make something like a hindenburg today with existing technology, we might have been a lot more successful than back then (as it goes way back to 1930s), there are still some blimps used occasionally, I also don't believe those use hydrogen(?), but they are not the "game changer in air travel" it was once seen as, although we can't rule out a comeback.
What about you guys?
Most of these issues come down to insufficiently advanced tech.
We're just now getting to the point where advancements in display and lens technology make it possible to get rid of the screen-door effect at no cost of clarity or FOV, for instance. (Varjo XR-3)
I think 2 major things need to happen for VR to be truly mainstream;
-Size needs to decrease, which increases comfort, so it no longer feels like strapping a toaster to your face. (Bigscreen Beyond)
-More quality content needs to be developed for VR.
PC gaming is mainstream as hell, and people easily spend over $2K on hardware, so I think price is kind of irrelevant (to a point) if people can shift the majority of their desktop gaming, and comfortably spend 10+ hours in VR.
I’m pretty sure Valve Software surveys say that only a very small minority "easily spend over $2k on hardware". Especially considering that VR would be in addition to whatever they spent on hardware already, and that these $2k would be on a single device instead of slowly upgrading hardware over time.
In any case, I see two possibilities:
Personally, I’m hoping for the first, and I’m expecting it to come by 2025.