It has ballooned and will continue to. There was even a story on here several years ago of a whole congregation in the US that went 'apostate' and started partaking, then was disbanded.
Beyond that, I wonder how many more that partake in private and aren't counted. I'm one of them, and I've read of others who do the same, because they don't want to put on airs or tacitly agree with WTs definition of what it means to be anointed.