I regularly play old folks' homes (I figure I'm old enough now myself that I don't have to be politically correct in my terminology when it comes to age), and I find people have always sung and continue to sing along with great enthusiasm to the World War era and other old 'sing-song' stuff, and I anticipate they always will, at least as long as I'm in the game, anyway. YMMV.

OTOH, I also put some fiddle into the act, and I've noticed in more recent years, that fewer and fewer people have the kind of gleeful response to it that used to be common. And it's rare now for someone to come up after to tell me that their father and all their uncles played fiddle ....