Linda and Steve have a point, why should we bother so much about the young demographic, but I have a different take.
What we know about youth culture is that it's mostly middle aged who spend much time trying to guess 'what the kids'll like'. We see it in TV and pop music (think 40 year old gay men trying to be 'hip') even in church movements (think 40 year old pastors in ripped jeans) as well as more notorious religious groups (Al-Qaeda, ISIL). Sometimes it works, unfortunately in some cases when it leads to exploitation of youthful naivety and ignorance, but often it doesn't: just attend one of my lectures.
However, there are two other characteristics of youth culture: it can be emergent, fashions popping up unexpectedly from those not paid to "know what the kids'll like", as well as cyclical. Who would've thought 20 years ago that in the era of the internet that a series of books with long, complex plots about good and evil would be so massive - 500 pages of long words with no pictures whatsoever!
So, perhaps we should be mindful not to thrash around too much with the county system in a frantic attempt to get down with the kids. There's a need to stick with a routine format that is bringing in families, however I still think that whilst the to audiences aren't what they were, terrestrial to coverage is more valuable than we think: millions still watch the drivel on the 4 main channels, not all youngsters are online all the time and anyway it is not a bad idea to reconnect with their parents and grandparents who are the ones who will pay for the tickets...
...also, classical music is unfashionable with the TV companies at the moment, but the likes of Andre Rieu sell out across the globe targeting the older audience who have the money. Who's to say that a Nigel Kennedy-esque star with street cred won't emerge in the future?