[secstate]

Yes. In the sense that Mastodon is decentralized because there is no one Mastodon server. One may accumulate more users or be the "default" for the community of users, but there is no Mastodon server (much to the chagrin of many new users).

We don't even need the hypothetical "it will defacto become..." because Bluesky Social was, up till now, the ONLY way to participate in the community. They had 3 million users before federation, and now we can start to hook into what they've built, but the idea from the start was clearly not built around federation and decentralization, otherwise it would have been federated from day one, as Mastodon was. They can HOPE now, that people accept the federation concept, but there's enough gnashing of teeth around the pain of running Mastodon instance that it seems really clear that going from central to decentral is, if we're being intellectually honest, a bridge too far for most to cross.