A good (ok, fair) rule of thumb is that with most other items, anything marketed as "limited" or "collectors edition" won't increase in value while anything produced and sold quietly and without hype (or was meant to be disposable) will skyrocket in the future. I don't know if this necessarily applies to cars, but it should. Perhaps then companies will stop manufacturing endless waves of "limited" vehicles and just focus on making the best examples that they can.
Finally, I am beyond frustrated with all of the "hypercars" that are beautiful examples of amazing engineering....that are locked away and never driven. Great examples of this are all of the new Bugattis (Veyron, Chiron and now Divo). The engineering behind these cars is mind boggling (with a price to match), but the point is that they were built to achieve a certain set of parameters, which quite sadly, most will never fulfill or even begin to. I fully understand the concept of "art", but "art" is form over function, thus I can't reconcile the concept of collectibility of such machines with the fact that the "function" is what is actually driving the price point. Perhaps cars such as these are not being purchased as investments, but more of the "I've got something that you don't, and won't ever have" mindset....but then again, and if that's the case, shouldn't it be flaunted by being driven daily?
Anyway, sorry for the "mini-rant". I've got a line from a song stuck in my head..."someday when I figure it all out, I'll be sure to let you know."