In my 3 short years in the bike hobby I've seen changes, but I see it as a good thing, it's expanding. In the last year or so I've seen more and more kids on old cruisers or their new stylistic counter parts, kids on their dad's old BMX and loving it. If the hobby is changing and evolving it means it's still alive and well, also means the "old guys" have done something right in passing on the tradition to the next generation of bike lovers, car lovers, or what ever the hobby might be. I've noticed it more so in the car hobby, since that is my main interest. When I was a kid in the mid 80's I started going to swap meets with my dad, seldom did you see a father and daughter walking around, now that seems to be the majority. I currently have a young son and he is already car and bike crazy, but if I have a daughter I will encourage her to be into both if that is her choice.
With the high end bikes not selling I only see it as right now the hobbyists that want and can afford one already have one, which in some ways mirrors the car hobby. The younger crowd doesn't have the means to afford them just yet. I'd say at 32 I fall into this still. I'd love to have a Krate bike of any year or color, maybe an older P.K. Ripper and nice '55 Chevy, however I have a young, growing family and the disposable income isn't there yet. So, to enjoy these hobbies I look to the cars and bikes a little farther off the main stream.
I know that the old cars I had while my wife and I were dating she loved driving my '52 Chevy truck that had disc brakes, power steering, a V-8 and an automatic transmission because she could handled it, my '49 Chevy Fleetline was a different story, she loved it, thought it was the coolest thing, however the cold blooded, dual carbed 6 cylinder and 3 speed on the column were a little more than she could handle. Same thing with the bikes, when I got her on an old Murray cruiser it was sloppy, the coaster brake didn't do good stopping with a bike trailer in tow carrying our son, however, once I put her on a big box store Huffy that is vintage styled, she loved it and now wants to ride all the time.