Predictions: Google gets broken up a la Bell, Twitter transitions to something decentralized to protect First Amendment principals, and Facebook completely collapses through legal troubles and user exodus. Silicon Valley collapses, valuations collapse, unicorns return to Neverland.
EDIT: And Amazon fails to compete once the real cost of business is accounted for and forced upon them, i.e. USPS. Small businesses gain advantage and begin to eat away at the edges.