The platform crossed the milestone last night, and it happened about a month and a half after the 25 million mark. Bluesky still has a long way to go to pass Threads, though; Meta’s platform has more than 100 million daily active users.
[Media: https://bsky.app/profile/bsky.app/post/3lgu4lg6j2k2v]
You say that as if any Mastodon instance was guaranteed to last several years.
The difference is that you can easily move to another Mastodon instance, and it’s designed so that when you do that your followers / followees come with you.
Except you can’t move your posts. Or, really, anything other than followers.