Yes they are, it's inevitable although in the case of Gamestop they are accelerating it.
Check Gamestop latest quaterly earnings report.
They made more money out of used games sales than new games sales and they are the number 1 retailer for video games in the US.
Publishers are getting more and more fed up with this ( a retailer shouldn't be more money out of a game than the people making the game) and the nail in the coffin won't be online pass, it's going to be digital sales.
I predict that next gen 90%+ of the game will be available as a digital purchase on day one at a reduced priced compared to retail.
And once over 50% of the sales have moved to digital the lower retail volumes will kill the stores...( the same way digital books just killed Border and they still represent less than 20% of overall book sales...)
What most people fail to realize is that you don't need digital to overtake the whole market ( which like some pointed out ain't gonna happen with slow broadband and others reasons).
It just needs to make enough inroad to reduce the volume of retail sales and then retailers whose whole business in based on volume will stop being profitable...( divide sales by two and retailers will have to asks themselves whether it's profitable to stock less known titles with low sales, some will stop and lack of choice will push customers away, same thign with used sales, divide sales of new games by two and retailers will have a slower pool of used games to work with and some titles will become increasingly hard to find used ( and as a result used price will raise).).
You'll still be able to order your titles online from shops like Amazon that don't have stock costs issues but it will be increasingly harder to find non mega-hits titles in your local stores ( exactly like what is happening to the books). You will always find the latest CoD or Mario kart at Wall Mart or Target......