Steam has done a very good two front assault on the used game market- first, by being all digital, it of course makes re-selling the games impossible, but at the same time it is delivering a market where people care less. Games are always available, always supported and, most importantly, relatively cheap. Super cheap if you wait for a sale. When buying games feels like good value by default, the used market is less relevant.
The only time I've bought used games is when I literally cannot find a copy of the game available by normal retail- and that's certainly a sales loss that no publisher, writer or designer can blame me for or claim they should have the money from. But Steam has done away with that by having older games both available and, generally, at a good price.
I think one point we can't ignore here is that, based on the technology of the Xbox One, Microsoft simply cannot allow open re-sales. That's because the games run off the hard drive and not the disc, so if game re-sales were allowed, people could sell their games and still keep them, which loses both the legal and moral justification (the first sales doctrine involves the re-seller in turn losing his right to the product).
So the only option they have is to build re-sales into their system somehow, which I believe they have said they will do. I think it would have been a much better PR move, though, if they had gone down a specific "XBox One will support re-sales!" pitch.