Anyone sane has left Xitter already and the crazies stay on their own platform, making the Web generally much more pleasant, as less and less sites link to Xitter.
Even assuming 25% of Twitter users are bots (probably a significant over estimate), and even if half of Twitter’s users quit in the next year, it would still be 150x bigger than mastodon
(Mastodon has ~1m MAUs, compared to ~421m for Twitter)
From my understanding, Bluesky (despite its recent growth) isn’t particularly big either. Threads claims to have a lot of users and I assume it would have the easiest time attracting normies, but I am still sceptical of its long-term viability. I feel like the people leaving X would have quite a bit of crossover with people who despise Meta.
So that leaves us with a fourth competitor, which is nothing at all. Anecdotally I think this is what I am seeing the most - people who leave X are just abandoning the entire concept of microblogging, since the point of it is to speak to a large audience and none of the competitors can really deliver that right now. The appeal of Twitter was that everyone (who was interested in microblogging) was on it; smaller, niche communities are fine for discussion boards and group chats but microbloggers don’t really want to be screaming into a void where most people will never hear them. Microblogging was never even particularly popular anyway (when compared with other forms of social media) and I wouldn’t be particularly surprised if the downfall of X eventually kills the concept for most people in society.
iirc when you sign up for threads it links your Facebook/Insta account and there’s no way to delete your threads account without deleting the whole thing, so their numbers are likely inflated