I know people interested in Norton/Triumph/BSA who were not yet born in 1976 and even more that were under 10 in 1976. Several of them got their first bikes in their early 40s and the bikes were older than them. So, I'm wondering how many Norton lovers on this site are old enough to have ridden a Commando when they were available for sale new.
Logically, those of us in the late 60s or older will die off soon and those with a lot of bikes may well have them auctioned off. In my case, my stepson would fight his sons (all in their 20s) for my bikes if I died now - no auction as they all have//want Nortons and Triumphs with a smattering of BSA dirt bikes.
So, the market may shrink, but then the supply is shrinking (bikes being destroyed/parted out) so I think there's a future, just like there are people who collect bikes that weren't available when I was born.
That said, it will likely never be profitable to restore and sell old bikes except for auctions where things are way overpriced for the non-auction market.