Gizmodo: Watch an Artist Instantly Create a Mirror With Liquid Silver Nitrate. http://google.com/newsstand/s/CBIw3LWW9DY
Silvered mirrors are some of the most difficult and expensive optical systems to manufacture. This method of creating a mirror could easily bring costs down, even for optics, due to decreased complexity.
https://www.christiedigital.com/en-us/3d/virtual-simulation/virtual-reality-systems/3D-collimation
You could probably also create a curved mirror with this method much easier.
One day, we may see an HMD that uses a Collimated half silvered mirror optic. The Expanse Virtual Cinema HMD was one such device that failed to meet funding goals. It traded stereoscopy for resolution. In a dual display system like the 8k, stereoscopy could be preserved.
The benefit of such an optical system is that the entire display’s pixels can be seen with no chromatic aberration, no need of lens dostortion, and so, no SDE, while also provding a large FOV.