Facebook is just to big to go down that fast in my opinion unless something really bad happens and reveals everything that they do. But don't neglect the fact that FB owns IG, WhatsApp, Oculus VR and many more altogether.

We all know how bad they handle our data but the real question is are people willing to give up FB and other related stuff? Well I think not, they are to comfortable with where they are at, same thing applies to google. Some people will stop using these/delete their accounts but majority will stay on them. If FB fails to keep its users occupied it failed its job as they are likely to move to other platforms.