First of all, most folks don't live in the Barrett-Jackson universe...
It's sort of like living on the next street over from a high priced neighborhood. If you want to sell your house, you are glad that those rich folks are raising the values, but you know you cannot afford anything on their street if you decide to move.
I've been watching Camaro (and classic cars in general) values out in "the rest of the world" market for years. Actually, "fair" or "good" values have climbed steadily, while "show" values, especially Zs, etc., have gone out the roof.
As to whether values will reach a maximum anytime soon on muscle cars...
I was recently at a classic car sale/auction in Charlotte, NC. There were hundreds of cars for sale. Seller's values were up $5K to $10K, but buyers were cutting that increase off the top and, yes most of the time, driving away with the car.
Up until a few years ago, most muscle car owners were considered "Young Upstarts" by antique car collectors. Their 20s, 30s and early 40s cars were rapidly increasing in value. Now, their market has leveled out somewhat (and muscle car values are helping them hold their value). In just a few years the 70s cars will fall into that "true classic car range of 35 years or older". Right now, you can buy most of them "cheap". And when they start trying to claim their place, all of us 50s and 60s owners will look down our noses at them and say things like "It's not a classic car without chrome". But the market, kids who are just learning to drive now, will give them value.
So, yes, I think muscle car values will eventually level off somewhat, but it will take a depression to make them go down. (And not trying to be rude at all,) if you decide to "cash in" now, but later want "back in the club", it WILL cost you more...
Besides, most of those B-J buyers never drive their cars!