I've been trending in this direction anyway, but next month Twitter will become an announcement-only platform for me. Personal prediction: there will be no mass migration to the fediverse or spoutible or anywhere else. Instead, a return to internet 1.5 norms is underway: smaller, more niche communities, many of them walled gardens. The global public square/water cooler is on its way out as an ideal.
Why do I think this? Partly bc Internet 1.5 platforms are having a renaissance, Reddit and Discord in particular. Most people don't want the entire planet to follow the conversations they have with their friends. That is a useful discoverability feature for content creators/media people (myself included) BUT there are ways to manage. Ppl will still go to Twitter, FB, Insta etc for news; posting announcements there will still have value.
What is happening now on Twitter is not migration; it's dispersal. People are leaving for a whole host of different platforms. As long as twitter remains an essential clearinghouse for breaking news and up to the minute info, it will shuffle onwards, but it's finished as an incubator of mass culture.
@GWillow This reminds me of what happened when Livejournal started becoming hostile to fannish activity: a slow scattering with no consensus of where to go next.