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.