I don't anticipate seeing many of the unreleased games coming out anytime soon.
Strangely enough, though, I've been hearing of a group that spends exhorbitant $$$ to buy unreleased games from collectors under the guise of themselves being collectors, only to turn around and release them to the public on the downlow. A recent DC release just happened that way, along with some Neo-Geo prototypes, so it's spreading across platforms quickly. I haven't heard of this kind of thing happening beforehand (other than you, of course, in an apples to oranges kind of way ). It's really struck a chord pitting gamers vs. developers over at ASSEMbler's forums.
I personally would give an arm and a leg just to touch Arena Football, much less have an on-cart copy.