You realize almost the entire gaming industry doesn't give a shit about them.
They still need somewhere to sell boxed games though. These chains would vanish without used. I still don't think they are in the business of kicking their partners right in the balls.
Gamestop would be fine just not their profit margins. Publishers could give two shits about what happens to used game companies. The only reason they still do business with Gamestop is the shear amount of preorders it provides to the publishers. Gamestop would still exist without used games but they also wouldn't be a Fortune 500 company without them either.