I think most instances will just have to block it, honestly. Unless it... provides fediverse access only to well-behaved accounts or something? This _could_ work, but would be a pretty bizarre user experience.
Assuming it just federates as-is, though, I don't think it'll last a day on most instances.
Yeah but how do you even define well-behaved? That can become complicated real fast. My bet is that they'll just allow people to follow an account using the classic @username@threads.net and they'll allow for export of the content and that's about it.
Assuming it just federates as-is, though, I don't think it'll last a day on most instances.