I think this may be a more complicated situation than it appears. The number of cars produced is fixed. The number of cars still licensed could be tracked down and determined (barring any illegalities). The "X" amount is the number of cars that are driveable (but probably need repairs) but are sitting in garages, barns, sheds, etc. that the owners have not licensed in years. Would these be considered survivors? IMO, yes, because there is a chance that someday, they could be/will be saved.
The other "X" factor is the number of them also sitting in garages, barns, sheds, etc. that are NOT driveable and the cost of their repairs outweigh the market value of the car. Then there are those cars that have been all but abandoned in barns, fields, etc. that are rusted heavily and stripped of parts.
Should they be counted too?
Well, if we were discussing 1969 Camaros or Plymouth Barracudas, many would say 'yes' because there are many fans of these cars that will buy a stripped out, rusted hulk and spend massive amounts of money and time to restore it. And sometimes, though not often, they actually make money when they sell them.
Since our cars don't have the fan following or the Barrett Jackson mentality of 'it's super rare and I gotta have it no matter what it costs', I don't think these 'parts cars' should be included as they will never see the road (under their own power) ever again.
Now, in the real world, TR7's and 8's show up on Craigslist and eBay fairly often and it took me around two years to find mine because I was pretty picky and wouldn't settle for 'almost what I wanted'. I still got it for a song (IMO) and that's one of the many things I like about these cars. I really don't have to worry too much about it getting stolen because no one wants these cars and there's no chop-shop market for parts. Now, if prices do shoot up astronomically when the general public realizes what a bargain they are (and relatively rare), I would be more than happy to double, maybe even triple my money, but I'm pretty sure that's a scenario that's not going to happen anytime soon.
In the meantime, I get to drive an economical car that turns lots of heads and I can't remember when I saw another one on the road unless it was in the general vicinity of a car show.
Aaron
1976 TR7 FHC (an ongoing project)