Today, Firefox Reality is available for standalone VR devices (like the HTC Vive Focus) and is a native Java application that talks to the GeckoView library, which is made up of components from the mobile version of Gecko, the Firefox web engine.
Firefox Reality for desktop will similarly be based off of the Firefox Desktop product pieces.
Note that there's a bunch of "Servo inside" - from small Rust components to the Quantum work including the new CSS style system to the forthcoming WebRender component.
I don't have anything to announce today about a Firefox Reality-branded browser based on top of Servo.