Bluesky / AT is the most successful open social network in history and the only one to become culturally significant. It has been adopted by presidents, celebrities, journalists, and mainstream users.

Bluesky has ~50M registered users and has sustained ~5M monthly active users for long while. There's no reason to believe it will fall substantially below this level.

It is also in the process of adding (decentralized) subcommunities, which I expect to be really cool and have a large impact on growth.