This is strictly my humble view of Facebook's creator, and the path left here.
On the path of technology development and nifty ways of using Facebook....Zuckerberg might be the guy to have as the chief and running the company.
As a business CEO, or being the figure to be dragged into some congressional meeting? No, he's simply not that guy.
I think by summer of 2019....after congress attempts to write various reforms into the data handling of Facebook....the board will meet and decide upon a bold new vision....which pushes Zuckerberg out the side door and he will be kept as a consultant-only.
The pain here for Facebook is that they envisioned using all this collected data for dozens of projects, and somewhere in the middle....was political conversation and converting people to certain agendas. You might sit there and laugh....but they expected to use it for bringing the 'right'candidates up (note: Democrats). Instead, they've now discovered that they released the user data to an organization that blended it into a product for Donald Trump.
I would suspect that Zuckerberg is sitting there in a furious state of mind. His product was supposed to be used for 'good' purposes and bringing in Hillary Clinton and so on. Instead, he gave the private data data to be used for Trump.
What Zuckerberg does as a non-entity of Facebook? He might go and start up another social media site. He might just retire to Costa Rica and sip fruity cocktails. He might even relocate to England and be part of the BREXIT world.
I just don't see him there at Facebook by the middle of 2019.