My predictions: Twitter will be the first of the social media Old Guard to collapse. Facebook will be the second. What follows will be a war of sorts between decentralized platforms like Mastodon and Diaspora and centralized, though "free speech focused" platforms like BitChute, Minds and Gab. They will probably split along political lines (Mastodon and Diaspora lean mostly left; MGB, right), and they're pretty evenly matched, so I don't know who's going to win; it may tie pretty closely to the political situation of the next four to eight years.