@Pawlicker I don't think it's reasonable to ever worry about BlueSky/Threads/etc killing the fediverse since there are so many people like me that no matter how genuinely good or convenient those platforms might be will never use them over fedi.
What could potentially "kill" fedi, or rather slowly phase it out, is a similar technology ran by hobbyists that doesn't have many of the flaws of fedi. I don't think Nostr is that technology, but something along that path could do it.