I can see it playing out fine either way, although it's certainly more turbulent federating if we are to see their content and it washes out the other communities (which to my understanding is unlikely since it's user based content like Mastodon). As others said, they already have our data, too.

Instead, I just wish the more... extreme communities didn't defederate already. I'd love to see Meta users react to Hexbear or Exploding Heads in an unfiltered, unadulterated way (or those much much worse instances that everyone defederates from). Instead they get us relatively tame, generally nerdy Lemmy users. I didn't even know what a Tankie was back in the before times!