I don’t think it matters that much. The users are very different. Most Threads users will be Threads users, regardless of what the fediverse does.
In the contrary, if a Threads user can interact with the fediverse, he/she could change his/her mind at some point because now he/she will be aware of the fediverse (eg Meta starts to put a lot of ads, many users will migrate towards the fediverse instead of paying Meta a fee).
As a consequence, I think Threads will stay « friendly » with its users in fear everyone migrates somewhere else. Otherwise, no one will leave Threads unless there are major issues (like Twitter or Reddit). Not federating because we fear the fediverse will not grow as much as a consequence is, in my opinion, the exact opposite of what will happen.
Just look at YouTube alternatives. People won’t leave the platform for peertube because they would lost all the content. Now, imagine that YouTube was part of it, do you really believe people would stay and endure as much ads ? I believe they would leave and YouTube would be forced to refrain itself in order to keep its users, and peertube would become much more popular.
TL;DR I don’t say we should federate at any cost tough. But I don’t believe the fediverse will grow because it rejects Threads (in fact, I think it will be the opposite). The question is more something like « Do we want the mass to be part of the fediverse ? » (with all the consequences like brands starting to put ads / communicate here, and a bunch of racists & cie that could possibly be impossible to moderate).
That’s what I said. People stay on YouTube because the content is locked there. If you could watch YouTube videos from Peertube without ads, I believe people would migrate and YouTube would be forced to be less aggressive with ads. I agree that’s partly because content creators do not post their content elsewhere, but that’s exactly why fediverse is nice : the content is everywhere, you can’t lock it into a single instance.
The reason for switching from Threads to fediverse is the same reason why you already left mainstream social networks. But people not aware of its existence, or locked there because the content and the people they interact with are only accessible from there, they can’t leave. That’s why many people keep a Facebook account, or why people tried Mastodon and came back to X a few weeks later.
In my opinion, if a platform can only be different from the other because of the services it proposes (instead of relying on its own content), people will be able to move easily from one platform to the other (and they will if Threads starts to abuse its position). You are afraid people will never leave Threads, but the truth is that as soon as they will have to suffer ads, they will try to find adblockers or alternatives to eliminate them. The fediverse can be this alternative.