Facebook is apparently working on its own operating system to replace Android, the new OS will be used in the companies own hardware.
This is devices like Oculus and also the Facebook Portal devices that currently use Android, Facebook wants to use it own operating system for these.
The new OS is been built by Mark Lucovsky who co wrote Windows NT, the company will keep its smartphone apps on Android, this new OS is just for their own hardware.
Although if the new OS works out for the company, who knows maybe we could a new Facebook Phone in the future with their own OS. It will be interesting to see what the company comes up with and what this new OS will be like