There's going to come a point in time, when collectors can not get what they want (unopened, boxed, manual, no scratches, etc.). It then comes down to how much cash it takes to separate a fan from the game they want to own. I would not buy a game if I didn't intend on playing it, so I guess in that regard I am not a true collector -- but if I see something I want, I build up a solid amount of determination to get it.
I own a few games, mostly disc-based, but I know for a fact I think every so often about which of those titles I absolutely could not be separated from. I'm going to play them again. When I was younger, I cycled through game via the Gamestop trade-ins, just to get the newest whatever game it was. I gave up some gems, and I regretted it when I suddenly found myself wanting those games back -- usually shelling out more than the original cost to re-acquire. I haven't traded in or sold a game since recognizing that as a possibility. How many others feel this way, and will not be selling games anymore?
There's a good chance, that with more and more digital collections, there will be some who are willing to part ways with there physical copies, with such huge cash gains on certain games. Still, there's the idea of owning something physical. Digital is only available as long as your console works, and as long as Nintendo, Microsoft, Sony continue supporting them online. For that reason, physical will continue to dominate the libraries, but there's no way that all collectors can get what they want. Expectations will lower, and the bar will be reset. Something, something, something... don't even know what the original topic was.