I agree w/ much of what you've posted and would add that you can point to the collectible automobile as a parallel for bikes. If a brand falls into obscurity, then there HAS to be something very unique about the product in order to garner interest among collectors. There were many, many car brands in the early 20's and 30's that came and went producing only a few examples, in some cases. The rarity of those various cars didn't guarantee their resale values. Similarly, take a look at Cadillac, whose products and brand became a joke throughout the 70's and 80's and is only now turning itself around. Yet, even as the brand was becoming a joke, V12 and V16 Cadillacs from the 20's / 30's and the V8 models of 50's / 60's saw resale values continue to climb long after the people who lived during the era had died off.
Mercedes Benz and Porsche are a different example where their products have always occupied the premium end of the segment. Their earlier products were both rare and differentiated (premium technology, materials, etc.) and their brands have always been aspirational. Nowadays, they crank out cars in much larger numbers and the resale values of their modern cars reflect that the laws of supply & demand are still in force - i.e. you can buy used examples for significant savings off their original prices, although even with significant depreciation, each of these brands is still a benchmark for resale value.
I think it's fair to point out that when something gains or loses in value, at some point you have to look at the actual currency involved. If you double a nickel, the value has increased 100% but it's still just 10 cents in total. When you have Kleins that sold for $3,000 15 years ago and they struggle to reach $800 to $1000 today, you could say - "well they've held 1/3 of their original value". But consider that there were plenty of bikes that sold for $150 brand new 15 years ago and some now sell for $50 - $75 if they're in good condition. So which was the better "investment"?
Sure the Klein is worth $1,000 today vs. $75 of the department store bike but the Klein owner lost more money on both a percentage basis and an actual dollar basis. At least it's probable that the Klein owner enjoyed/enjoys his bike more than the owner of the department store bike.
I believe that to hazard a guess on where the collectible bike market will be in 20 years is really just that....a guess. If there isn't any interest in a particular brand, or product, then value & worth evaporate. Fat, Yeti, Klein, and others have active cult followings which preserves their worth today but will those followings still be as active 20 years from now? Will new members enter the following and develop the same appreciation as I have for Klein? Maybe, maybe not. Whether or not the Klein following evaporates with time, I still derive a large degree of happiness every time I look at them, ride them, and share stories about them so I feel I win either way. I've also made investments in the past (MCI Worldcom, Nortel Networks, AOL, to name just a few) where I saw my investment go to zero. Yet, I didn't get any enjoyment out of the stock certificates of those companies. :cry: