I've never seen parallax emulated with head tracking that didn't have piss-poor latency issues. Not to mention poorly configured kalman filters that seem to always do too little or too much smoothing. These systems are fine for cute tech demos but don't belong in safety-critical applications involving multiple tons of steel moving at 100+km/h.
Before replacing mirrors in cars, why not start with making a TV "window" that actually works. Prove the technology in a real world application that isn't safety critical, then we can talk. If it's ready for use on highways, then it should be easy to mount a TV on a wall and provide a convincing experience of actually looking out a window.
I'd love to see a transparent A pillar but I can imagine the parallax issues (talked about in other comments here) would make them a bit weird.
Imagine a thousand foot tall semi-transparent google maps pin, resting lightly on the head of the person you're picking up, visible for hundreds of miles but only to those who are interested.
I have no idea if it will ever become feasible, but I sure hope it does.
Transparent material that becomes opaque to bright light (something like gamma < 1, gain < 1) in the direction of the light. So each point of the material is transparent or opaque depending on the viewing angle and respective directed light flow through it.
I think such a material could be engineered.
The 2015 Honda CR-V has a camera under the right mirror. When you turn your right blinker on, the screen switches to that view with an overlay for car lengths. It's kinda handy, but I probably wouldn't pay much more marginally for that feature.
They could also use complex optics like "plain lens" with a "fish-eye border", or highlight obstacles by boosting colour contrast or adding in non-visual sensor data.
If cameras are that much better we should be getting vehicles that use both (which we do for rear-view but not side-mirrors AFAIK).