I almost feel like a genre has to "die" at some point in order to live (i.e. gain relevance) again. Something that stays in the public consciousness past its prime gains association with being "something your parents like" and eventually "something your grandparents like", and these are bad associations if you want something to get wildly popular.

A lot of brands that have carpet-bomb "get everyone hooked at once" marketing campaigns, like Old Spice, end up with this effect where nobody wants to use the product since it's what their dad uses, and they don't want to smell like their dad. So Old Spice has set upon the strategy of letting its marketing go quiet for a few years, and then, pretty much once per generation, running a new fleet of ads claiming that Old Spice is "not your dad's deodorant", but is in fact best associated with buff 20-something men.

The same happens in clothing (look at e.g. 80s clothing coming back into fashion just as everyone's mom had finally stopped wearing it.)

Now, I've never seen anyone cite explicit evidence of it occurring in music as well, but it would fit the general mechanism. It might be why e.g. disco has mostly stayed dead (it's survived in the public consciousness with the image of the aging, pervy "uncle", a white guy with an afro wearing white suede and rollerblades, trying to retain his relevance); while genres like jazz are perennial (getting once again associated with being "young and cosmopolitan" at each turn of the clock.)

If rock can truly die—if we can let go of "classic rock" music stations and dads sporting worn-to-dishrags "rock concert" tees—and allow the ground of the genre's image to lay fallow for a bit, we might be able to sew something new there.