It's a truism in car collecting circles that people start out collecting the cars that they wanted as kids but couldn't afford until they got older. Some stay with that, while others wind up broadening their interests and collecting other cars as well.
I suspect the same is true of camera collecting, and that the "casual" collectors who want to buy an M3 now because they wanted one when they were teenagers back in the '50s are gradually going to dwindle as their population ages. Presumably, people who were teenagers in the '60s are going to be more interested in collecting mechanical SLRs. As for the people who are teenagers now... it's hard to imagine them reaching their 50s and awakening an urge to collect camera phones from their youth, but who knows?
On the other hand, people who collect cameras because they're interested in mechanical technology, rather than out of nostalgia, have always been a small group, but it's a group that's unlikely to dwindle further. Show a 20-year-old mech-technophile something really weird and funky, such as a Compass or even an Leningrad, and his/her first reaction is likely to be "What the...?" followed by "I'd like to have one of those." To this group of people, what's interesting about a camera is the way it encapsulates a set of unique solutions to a set of difficult problems.
It's possible that as more countries develop their technical education systems, we'll see an increasing number of technically sophisticated people who will be competing for the shrinking pool of desirable and interesting cameras, pushing up demand for good examples. At the same time, though, that demand will continue to draw "forgotten" cameras out of the woodwork, which I think is why we're seeing more interesting stuff on the market than we did years ago.
