They have already confirmed that the discs are worthless as soon as the game is installed. Obviously you can't simply sell that disc to GME 5 minutes later, that would be insane for MS to allow. Hence the daily DRM console check. Any license resale opportunity is entirely at MS discretion. They can choose to allow such a thing or not allow it, at any time. If they allow a third party like GME to get a cut, it's a cut of MS choice and at their discretion. Best case scenario, reduced margins for GME.
Don't think PS4 will save GME either. You can bet publishers will ship games with codes in the box so those discs are also worthless after activation.
Then there's the high expectation all games will be midnight available on digital, unlike the current situation.