I'm skeptical about this. I'm concerned that the rumors will indeed be true, and they do look likely. However, I sincerely doubt that gamers will go for it. If Sony and Microsoft do block used games, I think that a LOT of people will rebel/boycott the companies.
Even if these rumors turn out to be true, I don't think GameStop will be going anywhere. I think that they might have some room for being a "download station" for the gamers who do not have internet access. Though it'll definitely downsize a good deal.
Also, they can still carry some potential in the market, but not as a "mainstream" retail chain. They can start buying and selling older generations of games again. NES, Genesis, etc. Again, it'd be a major downsize, but they'd stick around.
I guess we'll have to wait and see what happens.