Regardless of the number of kits produced, WNW has definitely increased the number of modelers building WWI A/c . After years of shrinking numbers of WWI models seen at club meetings and contests, since WNW came out the numbers have been increasing in all scales of WW I models at clubs & contests--without a drop in other areas.
Again I'll relate the occurrence from the IPMS National Contest of a few years ago where WNW models were in abundance (and each year since!!!), among them there were 4 WNW HB W.29s entered and each one was by a modeler that said it was his first WWI model (one said it was his 1st a/c period) due to: low wing monoplane, no rigging (almost), colorful markings and the buzz about WNW quality and each planned on getting more WNW kits.
So it is not surprising that 3 of the sold out kits fit most of that description; the other 3 easily gobbled by us enthusiasts that knew what they were, the duellist (Fok/Dh2) a bargain much as the F2a/HB is again.
As to actual numbers of WWI modelers, personally whenever I make a WNW order it usually includes models for 1 to 3 others who either do not have: access to the net/ paypal /or pay me cash to hide the real cost from SWMBO --so who knows exactly how many are out there