I think the right question to ask is... how many racers will attend their NA's.
My round number estimate is:

With 70 teams. (50 F18 and 20 F16) teams on spin boats in 2011. 100 boats on sloops (60 H16, 20 TheMightyHobie18 and 20 H20, 10 Sharks) and 100 teams racing single handed (50 A class, 20 H17’s, 20 Waves, 10 Isotopes, 10 NF17’s)

So... that is about 250 teams racing at NA's

(If we could get them all to one event... that would be a hell of championship.)