I mean the 30's and 50's versions of the 500, but I get your point.
There are still small interesting cars that will be future classic. The Toyota iQ I mentioned is a classic case in point, and while not especially cheap it does follow the other principles quite well. The Smart will be a future classic too, if only because it was Mercedes attempt and failure at making a city car.
You may have point though in that cheap, basic, icons may be a thing of the past, especially since in the 50's Europe had just come out of wars and cars were icons not only for their abilities or charisma, but because they gave many people the chance to go to places and this won't happen anymore in Europe or the US. But the Nano, while probably not as able, could fulfill this role and become an icon 50 years on.