What I actually think will happen:
Lots of fuss and noise, then an unresolved detente for a while, then Threads starts getting widely defederated not for ideological anti-Meta reasons but for •moderation• reasons — and vice versa, as Meta realizes it can’t moderate other instances — and it eventually all fizzles because that headache is just not worth Meta’s time and money, it leads nowhere and they never really needed it in the first place.