Though GAGB members and forum users have now been separated, the best indication of how many users are active is perhaps the figure at the bottom of the forum home page, which currently stands at 515.
Most of those who belong to one of those groups also belong to the other, though there are a handful of exceptions in both groups.
The total number who voted in the committee elections last November was a disappointing 56 (cachers/caching teams, not individuals). That certainly doesn't give any indication of active numbers, as the forums have more logged-in visitors than that every single day, and I would imagine that many of the guests who visit are also registered users but haven't bothered to log in.
Do not go gentle into that good night.
Rage, rage against the dying of the light. (Dylan Thomas)