I'm one of the young ones.
I would say interest in black powder weapons has gone up in popularity, the number of people in the gun world who at least know what they are is quite a few. Every major sporting store stocks caps and black powder revolvers. However, us people who take these guns very seriously, We're a minority. But I dont see this being an issue, because first and foremost, we enjoy this stuff for ourselves. When I was a teen just last decade and was a little too obessed with this stuff for my own good, I took big pride in the fact it made me unique. We all do, it's what puts us in our zone. Black powder weaponry was my first love in firearms.
If you want to talk about the young generation not taking pride in the history of their country, and thus interest in frontier stuff is waning and people moving further away from the American way of rugged independence, that's a completely different topic altogether (but is indeed a issue with in of itself). But I do find even within this young generation there's a lot of people who like guns through video games. Games like Fallout: New Vegas and Red Dead Redemption has done a great job in making people notice black powder weapons more. Is this enough to make them actually interested in the history of this stuff? No. But at the least they learn to respect these weapons.
For me, what got me interested in black powder weapons was just the guns themselves. There was no movie, book or reenactment scenario that got me hooked. I just saw a pic of a percussion Colt revolver and it was love at first site. I was 12 years old just watching video after video on youtube of guys shooting the 1847, the 1851, learning about the Remington 58. One thing lead to another and I found myself deeply absorbed into these weapons. I would frequent Duelist1954s channel, and Capandball. of course this also lead me into other things, like military history, I was also briefly interested in reenacting but thats not for me. What is for me is enjoying the experience of using civil war era tech and appreciating them as both art, history and marvels of engineering.
So It's a very personal connection to black powder firearms for me. The only thing that'll get someone interested in these weapons is the person themselves, and it's a very specific type of person who likes all the accessories, the cleaning, measuring every charge. If the majority of people want to stick to smokeless cartridge shooting, then more true black for me.