The funniest possible outcome for Threads/Meta is that they decide not to federate with anyone after all (as well they might not) and everyone will have pissed themselves and got really fucking angry for no reason
They don't even need to federate with Mastodon to destroy it, just talking about doing so has turned the network into a non-stop bellowing and recrimination festival with all its worst traits proudly on display already, mission accomplished lads