Threads doesn't need to do an EEE attack. They've already gained many more users than the entire Fediverse. At this point, I wouldn't be surprised if they decided to not join the Fediverse at all.
I would never use Threads, but I would use a Mastodon instance that federated with Threads. I already see many journalists and content creators I like trying it out, who either stopped using Mastadon long ago or never even tried it in the first place. If Threads started doing things that negatively affected my experience, I would then switch to a Mastodon instance that wasn't federated with Threads.