I would say it's hard to predict. We've been over this before, and the same factors that drive collectibility will drive the collectable bike market.

Collecting as an investment involves scarcity of the item, speculation as to the rise in it's value, and can it be liquidated to realize a return.

Value for the money has no part in that situation, and that is still, IMHO, the driving force of C&V, besides an underlying appreciation for bike craft. The vast majority of bikes we discuss cost less than a Zipp wheel on a TdF TT bike.

I think C&V people like "underrated" bikes as much as the obvious winners. In that regard, my guess is that in 20 years, a Kestrel will be a C&V bike. We'll just have to see if they hold up.