Interesting point and it is quite impossible to predict the price of collectibles 10 years in the future. When I compare other knives to GECs, they usually come up short - with exceptions of course. I think it will be the shorter run knives in popular patterns which will be the valuable items in the future. I still enjoy my knives and likely will for decades to come. I recall when the secondary market on TC barlows rose to $100, then $125. I could hardly believe it. I've since been offered over $500 for a ppp TC, and it was tempting to let go but I would likely never have another. So I still have it. Now the more recent runs of TCs seem to be selling for around $200 give or take - an increase over retail in the 50% range. In this respect the prices already have leveled off, it is just those actual rare knives commanding ridiculous prices. The 38 American whittler was limited to 50 knives, there was only about 600 total configuration produced. I recall that being a formula for a potentially valuable collectible. Variants consisting of 250 examples out of a run of 2000 or 3000 are obviously less rare and demand could be higher but prices lower due to availability.
That's all I know about my take on the knife market. Prices could go in the toilet like with sports cards, plates, etc. Or through the roof, its shocking what truckers and farmers hats from the '70s and '80s can bring for example (need to go through the closets back home). When all is said and done, I buy and collect knives because I enjoy them and the hobby. If they go up, awesome. If they go down, I'll buy more.