I think there will be plenty of people maintaining interest in old cars in future. . . . There will always be people who like hands on old school stuff.
IMO, based on my 5 kids and all their friends - even though raised on brake bleeding and Italian tune-ups - those will be far, far fewer than today. And not enough to sustain sales. Poof. Once the well-off retired nostalgic boomer bubble bursts, there will be a vast oversupply, leaving depressed cars once again to rot. Add the other vectore and to me it is not a good picture. Again, just my opinion.