Foxy and Nathan have got it right. No problem with young seniors who support the sport, but they are always very few in number. Like Nathan says, it's the 40+ that are the backbone of vintage. Young guys get older and hopefully gravitate to vintage as time goes on. Our group of newer members come from the 40 and 50 demographic and are returning to dirt bikes as pressure of kids, career etc lessens.
John Kittle made the observation that "young guys are the future of modern motocross then as they get older become the future of vintage" I know there are exceptions, but this is generally true.
As Foxy observes, bringing in juniors on modern bikes (and their parents) is fraught with peril.
The growth of Vinduro is great and I see it continuing. I don't understand the doom and gloom though, 2010 Nats,about 160 entries, 2011 137, 2012 Classic (first after the split) 166, a (record), 2013 130 (at 7 weeks notice), 2014 Post Classic about 140. These numbers exceed the good old days mainly, so while we need to keep working at it things are not as bad as this forum suggests.
As has been said before, a rider, or sponsor who looked at this forum to get a view on how our sport is going would run a mile.
I will say though that this thread has been mainly constructive.