The demographic angle has been discussed. I think this link has been posted before:
Baby Boomers Created the Classic-Car Market—and Could Crash It – Feature – Car and Driver
I tend to think it's a legitimate concern, but I'm a "typical" boomer who got hooked on European cars during college in the '60's and have seen what the disposable income of my generation in our '50's and '60's has done to prices of all things "fun and special." The same argument is being applied (correctly, IMO) to large houses in suburbs. The appetite among millennials and younger is all about urban living and renting - and using UBER, Car2Go etc.
But as the prior poster pointed out, for most of us it's all about what we want and get out of our car passion/hobby while we still can drive. The major unknown, to me, is still whether the hard asset hockey stick over the past few years has brought in a bunch of non-hobby investors and whether this is a bubble that could end pretty quickly.
Case in point, of the 71 993's currently on eBay, more than a third (28) are turbos ranging from $150K to $525K. I don't think there are that many enthusiasts shopping for them just now - but a lot of dealers/owners trying to get out while the getting's good?