I have followed the muscle car markets for a long time now, and I think these cars will follow the old pattern where they drop with a poor economy to the point where a nicely finished car costs about the same as the restoration cost without the car. At that point (we are very close to it), the cars stagnate quite a bit and the only ones that trade hands are the hardship cases where the seller NEEDS the money so the buyer gets a steal, or the top shelf cars that the investors hold onto. Poor performance in the stock market tends to stabilize the "investment grade" cars as some investors turn to tangible investments like gold or some types of art.
As a person who enjoys driving the wheels off of cars and investing in stocks and bonds, this is both good and bad news. The good news is that if you want a really nice car to enjoy, the prices will be bottoming soon making them more affordable than they have been in a long time. The bad news is that there is obviously less money to be made by restoring these cars because labor and parts prices generally don't fall with the car values. Less money to be made means fewer restorations being done means fewer nice cars exist and fewer restoration products are developed. Right now we are in an interesting spot. The availability of cheap Chinese labor and the "development to market" times of significant reproduction parts means there are more restoration parts available than ever before and at better prices than any sane person should expect. Couple this overlap with the falling prices of these cars, and the guy who wants one, and then wants to make it his version of perfect is in a better position than I can ever remember seeing before.
While development and production of reproduction parts will undoubtedly fall off, and our economy and society will bear the eventual cost of all this "cheap" labor, there has never been a better time to acquire one of these cars and drive it. IMHO it is also a good time to squirrel away some of the more "damageable" parts while they are still being offered.
The prices will level out, but it might take some time yet because of the looming recession. After the economy levels out the prices will rise again, but it may take a while to see the values we had a couple of years ago.
In summary, get 'em while they're not as hot.