I think this only hurts Facebook for the short term, not the long term. I don't think most people are too concerned with privacy issues, I think most people realise that Facebook is free to use so there is a trade off. That trade off is a loss of privacy for the users but they don't have to pay to use the platform.
I think we are already seeing Facebook start to mitigate the problems, with Mark Zuckerberg already issuing a statement on how the company will change and that this will not happen again.
I think that Facebook will face competition from block-chain solutions like Steemit, though Steemit is slightly different to Facebook in many ways. I could easily see a decentralised system giving users monetary reward for content and the ability to control their own data as the ultimate Facebook killer.
But as I said earlier privacy issues their own are not enough for Facebook to be toppled from the No. 1 spot and block-chains are not quite ready as yet but the clock is ticking.