Not less than 1,000 and probably closer to 1500 or 2,000.
If you just count paid members of the class associations you get 1,000.
If you add in casual racers, you'd approach 1500.
If you add big boats, you'd get closer to 2,000.
The percentage that convert to the multihull MPP membership is paltry.
I fully agree that we are destined to die a slow and painful death if we don't do something to bring in new blood. We have one or two class championships that are growing and all others are shrinking. Fleet sizes follow pretty closely, even if you include fun sailors.