Well just look at what happened with XMPP and google: https://lemmy.world/comment/906346
And even if we don't defederate, I doubt anyone in threads will notice us local instance users and contribute at all to our growth. There are 30 million+ of them backed by Instagram and like what, 10k of us? They just have too much weight to throw around.
Hell I'm not even convinced reddit is going to die and Lemmy is going to continue to grow. Just look at their front page. Absolute nonsensical drivel still gets several thousands of upvotes and hundreds of comments, while any Lemmy instance is lucky to get 100 upvotes and 10 comments on a popular post