No one will go anywhere. Just like all the people who said they'd move to Canada if Trump won. and they never did.
If there was an alternative I think people would.I could see Zuck starting a Musk Twitter alternative and most people switching.People looking for a Twitter alternative due to Musk gives FB a huge opportunity to enter that space imo.
Musk wants Twitter to be something it is not and Twitter’s success is because it is not what Musk wants it to be. The confluence on Twitter of leaders, journalists, nations, corporations, et al depends on some semblance of civility. Once those guide rails go so will the valuable users. Now you may argue that Musk will only poke around the edges but not make Twitter repulsive (like Facebook is) and that is possible but somehow I doubt that is his vision. We’ll see. But as far as building a Twitter alternative that has some degree of norms if Twitter falls off, there would definitely be a market, unlike what Trump is trying do with Truth social - there’s not much of a market.
The hardest thing about an alternative Twitter has always been getting people to switch. People are lazy. I believe if people decide to bail, it'll have the same effect as when some conservatives tried to bail. Went nowhere. And facebook is dying.