At current rate it will 50M in 6 months.
eg. I personally had more than a dozen accounts
Most users signed up by downloading the app or visiting the web site and created a single account.
As a point of reference, the official Google Play store independently verifies that the Bluesky app has had 10M+ installs.
https://play.google.com/store/apps/details?id=xyz.blueskyweb...
There are no official stats on the iOS app or web but those are both likely similar or larger sources of users.
The reality is that a significant chunk (>50%) was Blue MAGA, or turned off by them, and I see little prospect that they will reactivate. Outside of the Bluesky echo chamber, there is a deep brand association with Bluesky being primarily political refugees. They see Bluesky as the left-wing Truth Social. I've asked hundreds of people IRL if they have heard of Bluesky, they are far more likely to have this brand association than to have heard of "atproto" (more than half vs 1-2% / can count on one hand).
Right now, Bluesky has one large community, which is already great for some people but not most people. Once Bluesky adds Communities, new communities can form, making it interesting to the other 90% of people who were excited initially and then turned off by it being "one note".
If you'd like to crawl the network to get real data, I built this a while ago https://github.com/verdverm/atmunge (it will take a few days to get sufficient data to do analysis, due to rate-limits)