I think the sales numbers we've had shared with us show that trendy twentysomethings aren't driving film sales singlehandedly. Kodak reported a 15% increase in pro film sales last year, and I can assure you that most of these kids are not loading Portra 800 into their Holgas. They buy Lomo branded film, they buy expired stuff on eBay, or they buy whatever's cheapest. 9/10 times I ask someone with a Lomo camera or an AE1 what they have loaded, they can't even give me an answer.
The increase in pro film may be due to the decrease in available expired stock, yes there will always be "expired stock" but the last of the big chunks of older expired emulsions are sort of lessened and the remaining expired stock is from emulsions which are still being made.
That's just a guess of course, but I've noticed a trend on eBay and there's less of the old stock out there.