I use an "antique" Itronics ITB100-HD since Xmas 2012, and the wonder is that they work as well as they do. This really is the essence of miniaturisation!
Yes, the things you see!!!!!!!!!!
Unfortunately, they have severe limitations, and I think those won't be remediated without a huge price rise, maybe looking at $500-$600, but that would be ToR with 1080p@30fps and in-built GPS. Mine won't resolve rego plates at further than 10 meters, usually closer, and capturing rego plates at night is hampered by poor exposure control--the plates are reflecting all my headlights straight back into the camera! (I have to off the lights for a couple of seconds...) But I have a new and very deep respect for my eyes and visual cortex now!
I note that in Russia you can't get insurance for your wheels if you don't have a dash-cam installed, which leads me to wonder why South Korea is THE Go-To Place for a good one?
But at (say) Au$150 each installed, I'd say it will be a while before auto manufacturers fit them as standard. Remember your Reversing Camera is actually fairly primitive, and has (AFAIK) no recording ambitions or ability, which means you never need to worry about SD card maintenance. OTOH, if I was running a fleet, there would certainly be a ToR model in every unit, and inaccessible to the drivers. These could be set to download the trip automatically on return to base or selected destinations, the same as fuel and black-box info.
Ay replacement time, I'm not sure I'd stay with the "discreet design". Korean philosophy is to show them off, and the larger form factor I feel would allow a bit more robustness and and performance in the design, especially in times of poor vision.