I think marketing platforms will always look for the users and their time/dollars. I believe Facebook is on the downfall but it will be a slow one as the tech savvy and those who deeply care about their privacy (or are even aware about Facebook's practices) make up the smaller part of the market. Hopefully things will change for Facebook and they'll be able to recover from this but cultural trends, in my opinion, say otherwise.
I think with technology, the barrier to moving from one platform to another is quite low. So people can easily move.
If we look at something like Netflix, no adverts but very successful. Could this be the trend?