Really looking forward to the the stereo rendering of non-WebGL content, HTML+CSS, which the Mozilla team is working on. More challenging path to figuring out but will open a lot of possibilities.
It's something we're looking into, but will take a significant amount of investment in platform (two very different parts of the rendering engine suddenly have to communicate).
For now, it's very low hanging fruits for content creators or engine developers to work with WebGL. It also doesn't hurt that it's much more performant.
On the other hand, it hurts accessibility.