Too late IMO. Twitter the incumbent, Threads just popped up out of nowhere with a whole heap of users.
People switch when other people switch, generally. Those tired of Twitter now have an easy place to call home, there's not going to be any momentum to then want to switch again.
Mastodon tried, and did get some following, but IMO is too complicated in concept for the common user. Bsky on the other hand just blew it.
One of the main open questions is how abuse will be handled. Mastodon is operated by volunteers with little extra time, in the worst case you handle abuse by just de-federating from an entire instance. Saves time for Mastodon mods. I don't think you can do that with Threads?