That seems logical, but the thing is, a collector's DVD market already exists. Certain Disney films go for high prices on Ebay, and MST3K the movie can be worth up to $100... and that's for the official DVD, which came in a cheapo cardboard case and had no extras to speak of. And this is despite there being a fan-made "special edition" which is filled with extras!
Yes, and those prices are suppressed by the fact that the materials are available elsewhere at a lesser price -- especially in the long run. Draw two sets of supply and demand curves for what we'll call the Legitimate Market and the Gray Market.
On the left, we see the supply and demand curve for "legitimate" merchandise. The supply is fixed, because there was only a limited release of Star Widget. Let's say the demand is provided by legitimists, who demand "legitimate" merchandise, collectors, who speculate on the value of scarce items, and the ignorant, who aren't aware of the Gray Market.
On the right, we see the Gray Market. The supply is practically infinite; assume data copying, transmission, and storage is free. The demand is provided by illegitimists, who don't care much about copyright, and are also sufficiently online as to be aware of the Gray Market. Illegitimists can freely enter the market, both supplying and consuming, through P2P networks. Keep this in mind: Possessing one of these goods does not prevent others from possessing it, too, and the supply is correlated to the demand.
Over time, consumers move from the Legitimate Market to the Gray Market. (There's some movement in the other direction, too; in the case of out-of-print media, I'd bet it's mostly from Legitimate to Gray.) With every legitimate or ignorant consumer that moves from the Legitimate to the Gray market, the demand shifts left and the price of Star Widgets in the Legitimate Market drops, but it remains unchanged (practically free) on the Gray Market. Collectors are left trading plastic discs with each other. Over in the Gray Market, the supply grows or shrinks with the demand, providing just enough to maintain the equilibrium price (practically free).
As for "stockpiling" Star Wars DVDs, that's just retarded. They're not valued consistently; Darth Fanboy might think the set is worth sixty dollars, but I'd value them around five, and less each year as more fan versions and official versions are released. Speculating on Star Wars DVDs is just gambling that there will be enough Darth Fanboys to keep the collectors' segment of the Legitimate Market afloat until such time as you're ready to cash in. There's much better ways to invest your money.
Oh, yeah. Remember laserdiscs? Laserdisc sets could run a few hundred dollars when they were first released. Unlike DVDs, they can not be perfectly copied. Search eBay for them now. And I guarantee you that a complete Definitive Collection is ten times the "collector's item" than a bunch of surplus special editions and the GOUT.