Meta just announced Horizon OS (without saying what it will change) and the Quest/Horizon OS is both pretty good technically but also infuriatingly artificially limited. It really doesn’t looks like Meta is going to give up control in this platform anytime soon.
Meta uses Android for the Quest.
Will Meta adopt Android XR instead of maintaining their own Android fork? Possibly, possibly not. But they are definitely an Android-using company willing to take on the Apple Vision Pro seeing as they are already, you know, doing that.