[REAL 1]

I think that to become collectible the model has to be out of production or at a minimum if the car is still being made it is superceded by something substantially different, i.e. Porsche 993s superceded by 997s which were now water cooled or even better the manufacturer has to have gone the way of the Doe Doe bird ala DeLorean. This is just stating the obvious though. However, I think initial desireability is likely the most important ingredient. The DeLorean while limited in number and no longer being manufactured in any variant was never really a desireable car and still isn't. DeLoreans are still rather cheap. I don't see them far removed from the Bricklin. Limited in number, not being produced any longer in any variant but still not very desireable.

Jamo mentioned the Shelby Series 1. I had also thought of the Series 1 as having collectible status in years to come for a number of reasons.

Yes my intitial question really focused on production cars not really customs like Boyd Coddington Hot Rods.