I watch the car auctions quite often, I'm actually a big classic car enthusiast...
In my family we have:
'22 Model T
'26 Model T
'30 Model A
'34 Ford 5-window coupe (rebuilt this with my dad from ground up)
'49 Pontiac
'65 Mustang I-6 'vert
Now I'm not claiming to be some kind of expert, just saying I've been around these REAL classics and been to auctions and am in multiple antique car clubs.
For a car to really be worth a lot the car has to have some kind of nostalgia. The old 50's and 60's cars were when speed was becoming a very big deal and car manufacturers were competing to make their spot in racing and hotrodding.
So yeah, the old Camaro's and Mustangs (even rebuilt) are going to be worth money. Almost always, these cars are restored to 100% original. And can be considered "stock". Those older cars bring in money partly because of the era they are a part of. The 60's model Mustangs and Camaros, were the start of the pony car wars. They were also made in the time where you had multiple v8 engine options. Not just v6 or v8, but "do I want a small block, big block, or Y block?". This is why I ask, "how do you compare the 60's models with the FOX bodies?". Yes, the FOX played an important role in hotrodding, but they were put out in the 80's which is a time that isn't highly thought of and they have that 80's styling. The earlier FOXes are going to fall in with the Mustang II's since they were lacking in performance and styling (some might disagree with the styling thing, but you catch my drift) but the later model FOXes have a better chance of making money.
The only chance FOXes have to make money is going to be way on down the road. More and more FOXes are being torn all to hell, thrown on the track, wrecked, modified beyond recognition, or even slightly modified. So the more time goes by, there will be fewer and fewer FOXes in good shape and left unmolested (not even muffs and/or simple bolt ons). These COMPLETELY stock FOXes and probably the stock special editions I can see bringing in some good cash. But other than that, I wouldn't hold my breath.
Again, I don't claim to be some kind of expert, and I could be COMPLETELY wrong on this. But no one truly KNOWS until it happens (or doesn't happen).
Sorry for the long post, just trying to get the point across.