There's no way to know, but my own home computer lab has become a bit of a sanctuary where Amigas can find safety from the cruel, hard world. Got six live ones and two dead ones at present. (Need me a cheap 500 next.) The dead ones have donated vital organs so that others might enjoy a better quality of life in their senior years. (Have I carried the metaphor too far?)
Seems there are more Amigas in use than actual users, as so many people have multiple machines. A measure of the activity by unique users on all the fora might give an idea of how many users are hyper-active. I'd love to know how many Deneb USB cards get sold as another type of measure of the enthusiasm for the classic hardware. Looks like I was lucky to get one of the first batch that was sold out at AmigaKit.