This question comes up multiple times per year and the answers fall into a few categories:
The values will plummet as we get older and nobody wants these cars
Who cares, I've got mine
They'll always be worth money
Etc.

Yes, there is a finite number, but still enough cars for the people who want them even though some who want cannot afford. The truth is that those of us who have been in the hobby since the 1970s or 1980s are fast reaching an age where wrenching on them just won't be possible or enjoyable. The truth is also that there are younger folks who also want these cars and some of them have plenty of money. Prices on mid-range cars (like my GTS convertible) may fluctuate some, but I believe its rarity will always equate to some value. Low end cars seem to have much higher asking prices these days than I would expect and these cars (some of them) seem to be moving. I see plenty of younger folks with an interest in these cars. What far too many fail to realize is that WE are a small percentage of boomers who still have these cars.

I think the hobby is fine. I don't find myself worrying about the value of my cars as they will go to my sons at some point in the future.