I think this is a good point, but I think the fedi community is established enough to bring people in when threads starts federating. If people show others tools like mastodon groups, following hashtags, etc it could encourage users to interact enough with outside instances to keep the federation necessary.
That’s the big question I think, can we convince new threads user to want to be apart of the fediverse? The door is going to get opened between the two communities and we need a substantial amount of cross-instance participation to justify Facebook not being able to defederate or make breaking changes without angering their user base and jumping ship to a non-threads instance.
I’m hoping corporations start their own instances (like nytimes makes an instance for its main account and its journalists) and institutions like universities make their own instances as well (there’s so many .edu emails, there should be .edu fedi accounts). This prevents their posts being governed by a big entity like Facebook and prevents a Twitter style enshitification.
From a normal user standpoint, follow your friends on threads, talk to them about how they don’t need to be on the threads app, and encourage posting/replying between instances with those around you.