What exists now is Mastodon, which is tiny compared with siloed social media, and also a few other platforms, which are tiny compared with Mastodon, and which partially interoperate with each other and Mastodon through ActivityPub. But only partially.

Among these ActivityPub-compatible platforms is Threads, which is already a bajillion times bigger than Mastodon.

Also, hanging off this tiny ActivityPub archipelago is the island of BlueSky, which is I guess not part of the fediverse because it doesn’t use ActivityPub idk why isn’t it connected to Mastodon?

The only people who care about this kind of thing are a few foolish nerds, among whom I include myself.