Dave, why do you think that enough of/any of todays teens will eventually come to folk clubs? If that was the case then there wouldn't be a problem, as every year there would be a natural refreshing of the audience, as people the reached the "folk club attending age" (whatever that is) and replaced the 70+s who left.

In addition, the implication of what you say is that folk clubs provide "something" that is unattractive to people under a certain age and atractive to those over it, which I think is questionable.