Stereotypical musings about Snow Crash's Metaverse aside, Vukićević describes where technologies will need to go in order to support future VR headsets. Unsurprisingly, support for VR in web standards such as HTML5's canvas element, WebGL, and CSS 3D transforms will serve as the foundation of browser-based VR content. Vukićević also wants to ensure that VR content remains device-independent, "beyond [knowing that] there is one and [that] it has certain standard rendering characteristics." The test builds of Firefox can accept sensor input from VR headsets and render content to them.
Mass adoption of VR is probably a few years off, but it's good that Mozilla is developing tools to help conceive a VR-aware web. If you want to get your feet wet with making such content, you can download the VR-ready builds of Firefox from Vukićević's blog post. The post also contains some starter code for communicating with VR hardware, and it provides some bug reporting tips.