Following the community vote we're still defederated with threads and have no plans to change that.
Lemmy 0.19 introduces the ability to make your own choice by allowing you to defederate with threads yourself regardless of server though. With any server on 0.19 you can go into your settings and add threads to your blocked instance list.
I think it's also important to point out that they're only testing federation with mastadon at this point, there's nothing to say they are in a position to federate with Lemmy. If/when that changes this community can have further discussions on the subject.