Just my opinion but it depends on the rarity and condition and it's influence on car culture.
Mustangs, Corvettes, Camaros and other muscle cars from the 60's are in such high demand these days because people in their 50's-70's want the car that they grew up with, either their dad had one or it was their first or second car they owned.
More than just the performance of it, they became legendary cars, the example for their genre of the muscle car, and muscle cars were a big hit back then.
You have to keep in mind what cars are here with us today to what will be around 30 years from now. Will the GT86 be a big get? Well it has a few things going for it. One, its a niche car, only 9700 BRZ's were made to US/Canada spec in 2013, and only 4500 in 2012.
http://www.goodcarbadcar.net/2012/05...s-figures.html
I have a 2013 BRZ, Limited, Automatic, in Galaxy Blue.
Do some math...
9700
1/2 were Limited trim (= 4850)
1/3 were Automatics (= 1616)
8% were Galaxy Blue (= 129)
Galaxy Blue was discontinued for BRZ after 2013.
I can't remember where I heard the stats for trim, trans, and color but that's what it was.
My car is in a group of only 129 examples for 2013, and were not made again (at least with that color). If I include the same math for the 2012 year, only 60 such cars were made. If you own a 2012 BRZ Limited Automatic in Galaxy Blue, you own a collector car. Do not sell it or trade it. In 20-30 years you will have an auction level car.
I don't intend on getting rid of my car, I will keep it as long as I can as a future investment, and see what happens. I'll store it away if I have to.
Back to what makes a car valuable in the future, another big consideration is rarity. If 30 years from now, a car that only had 60 produced in a year, and 129 the year after that, and were discontinued in that color after that, that means only 189 examples were EVER made. How many of them would be in a good enough condition to sell then? Maybe less than 50 of them? If you own one of them in pretty good condition by then, that's a rare car, and collectors buy that like crazy, regardless of what it was. You never hear of a rare Honda Civic. Why? Because Honda made millions of them since they started. The only rare one would be #00000000001, or a manufacturer special edition, limited runs like the Mugen RR, but even those aren't as rare because they were
intentionally made rare by the manufacturer.
Unintentional rarity from limited manufacturing or discontinuing something makes a car so much more valuable because it wasn't intentionally made rare. Does that make sense?
I honestly believe that BRZ's and FRS's will be collector cars, depending on who the buyer is. Corvettes have sold a few million since they started? That means there's a few million prospective buyers of a rare Corvette, and they will clamor over each other to get it. The FRS/BRZ only has what, less than 100,000 for US spec made? Not many buyers.
If they keep making the BRZ for the next couple decades, then yes there will be enough buyers to increase the value.