They’ll move to the ActivityPub protocol. This is almost guaranteed, as it will provide the platform protection against privacy and anticompetition laws that are currently being drafted against monolithic social media platforms.

But it won’t stop there. They’ll use the protocol, but Instagram doesn’t, so Threads will always have “extra” features that aren’t a part of ActivityPub.

This means that while ActivityPub users will be able to migrate to Threads and preserve their connections, Threads users won’t be able to move elsewhere in the Fediverse and keep all the components of their service.

And Threads already dwarfs the rest of the Fediverse in users after less than two days, despite not being available in Europe due to incompatibility with real privacy laws.