Meta announced that users on Threads will be able to see fediverse replies on other posts besides their own. In addition, posts that originated through the Threads API, like those created via third-party apps and scheduling services, will now be syndicated to the fediverse.
On paper it should play well, it appeared as Mastodon would on my Mbin instance. A lot of Mastodon instances have preemptively defederated from Threads though, so you need to shop around.
Or just don’t federate with threads. Embrace, extend, extinguish is a thing