The odds that Meta will siphon off a federated Mastodon server’s value seem smaller than the odds that people will just ignore Mastodon because they can’t engage with it via a higher-profile platform. Which is fine if your goal is keeping Mastodon very intimate, but this isn’t Google Talk and XMPP in 2009.
I am also very very unconvinced Meta will ever add ActivityPub support in any pragmatically useful way https://mcnamarii.town/@mdm/110667509260144960
Administrator (@[email protected])

@[email protected] Mastodon admin here -- I didn't bother blocking Meta, because I have no belief that Meta will ever make Threads federate with the Fediverse at all. In a month, Threads will have 5X as many users as all of the Fediverse. There's no incentive for Meta to even get ActivityPub working on their end.

McNamarii Town
@thedextriarchy I think it’ll happen because the normies will probably want that nice instagram integration. Meta won’t be losing too many people to third party apps. Personally, I enjoy the rss style activity pub feeds. So I’d love to be able to combine both.