"Facebook aren't going to want to take people off of their platform. Speaking from a web development point of view, they're the least flexible when it comes to integrating into your site, as they want you to come back to Facebook rather than stay on the third party site. I don't see that changing. This would be a perfect gateway into paid accounts on Facebook that give you different tiered access to content that's watched on FB."
Based on the above quote, you're clearly not aware of how it works. Facebook have a native Facebook videos app, where I watch Facebook videos all the time, on my TV, built right in, in 4K - I can't do anything but watch videos on that app.
Facebook also own Oculus, Whatsapp, Instagram and loads of other platforms that do not require Facebook.
Don't have a TV that has it built in? Buy a fire stick.