We really shouldn’t take this Meta thing lightly.
They could offer the slickest interface and keep people locked to their friends. That interface can use protocols that make it difficult/impossible for non-Threads instances to play ball (ooh this cool new feature is only available through the Threads app; Oh, mybasement.world.ml.xyz can’t read that content). There are many ways to Embrace, Extend, and Extinguish, we’ve seen Meta do it before (e.g. XMPP), and I’m sure we haven’t even thought of some ways Threads could EEE.
I think defederation from Meta’s instances is probably our only option to protect what we have.
That just gives meta more reasons to make extensions to activitypub, or a fork, without consulting others first as nobody’s even working with them…
If they’re federating then at least they have some interest in keeping things compatible