I don't think anything much will happen to Facebook, not that many people are really aware of what happened, and in the sale of personal data to outside companies like Cambridge Analytical, the typical reaction is that nobody is swayed by email political advertising. So I don't see this as a big blow to Facebook as long as they keep their members they are OK, how many people have deleted their accounts? Not as many as you would hope.
Apparently 9% are saying they did or will do in the next weeks. We’ll see if they really do :).
Facebook has well over a billion accounts, I wonder if over one hundred million have actually said they will delete their accounts.