Bear in mind HD's "Project LiveWire", which is looking more and more like an eventuality (instead of an interest-generating PR stunt). Clearly, they realize the 'next big thing' in biking is electric propulsion and they're busy applying for patents left and right, revealing that they've been very busy in the R&D departments.
Before we raise the bugles and hoist the casket, remember that HD sells more bikes quarterly than most other manufacturers move in a year. As well, their 'bobber' lineup continues to proliferate and its aimed squarely at the beards n flannels crowd. But a sales dip, even a sales decline doesn't change the fact that HD's bread and butter continues to be the post-50's crowd. More moneyed, more time on their hands and no kids. Just get them onto the sales floor; from there HD wows and sells them with one of the best dealer networks in existence and one of the most successfully crafted brands in marketing history.
As for BMW, they have been reaching deeply into the pre-50's market for some time now. Their lineup has never been more exciting, with newer, affordable (and smaller cc) models forthcoming they're gunning for much the same thing as Harley-Davidson: brand indoctrination and brand loyalty.
Motorcycles are an interesting product, really. Totally 'unnecessary'*, they are for most people a hobby, a diversion - a lifestyle. The marketing of them, therefore, continues to prove fascinating.
*Asia, et al, notwithstanding where people rely on cheap, reliable bikes as their primary means of transportation.