Not sure if Facebook is stepping away from AR/VR. Oculus/ Facebook reality labs is still hiring plenty of folks in the optics/ photonics world.. even making announcements over the last week on open positions.
If someone wants to look how Microsoft is also doing from a engineering PoV, watch this cool video from Marc Pollefys from ETH Zurich/Microsoft. It was made for a technical-minded scene and shows the behind-the-scene, some potential issues (privacy) and where it is going next https://vimeo.com/380218937