There's a tremendous difference between publishers being able to develop their own DRM method (as they currently can on PS3/X360) and the idea of embedding a method into the very ethos of the console - both logistically and in principle. If a DRM setup does become unanimous across all titles over the course of the next 7 years (which is a possibility) then it will be measured against what MS has opted to do, and will be designed to overcome the problems MS are locked into. The chances it would end up being less desirable to the consumer are negligible.
Moreover, we've seen the extent of the reaction against MS's DRM. We've read the opposition in so many articles, interviews with various 1st and 3rd party execs. We've heard it too, in the Sony press conference. The most important indicator will be seeing the sales figures after 1 year or so, but those figures will have a profound effect on consumer rights in the long run, and the early adopters who provide those sales are the ones who have been most vocal. If a huge proportion of the PS4 ownership is going to have been motivated into their choice by concern for their rights, which publisher is going to happily throw themselves in front of the social media train we've seen running away with itself over the past few weeks?
Especially when there's no concrete evidence that used sales damage publisher profits?
Agreed, it's not conclusive that the used games market cannibalises on overall profit of the publishers. It's too dynamic and interlinked to tell for sure. Sure Gamestop makes a billion dollar in profits out of trading selled games, and publishers think: "Why, I could have that profit, it's my games".
But then why don't the publishers build up a used-game-retail-chain or why don't they buy Gamestop and go from there?
I think publishers should be more relaxed about it and see Gamestop's profits as a reward for Gamestop's service, for offering and organizing a retail-chain for trading games.
Minus that profit for that retail-chain, all the rest of the money ends up in the hands of the publishers as new games-buyers buy more because they know they can sell on, and used game buyers are partly financing the new-games-buyer.
The much bigger question is the future availability of games, if games are only useable through licences, there is a danger for games to become obsolete in five years/ten years after we bought them, because the licence got changed or simply not supported anymore.
Discbased games have that assurance that even in say 10 or twenty years I could play these games out of nostalgy or for historic reasons or just to show my kids or grandkids what limited but charming games we were playing a long time ago.
These are concerns that need to be adressed when going all-digital, there should be a possibility to record digital games if we want to preserve them, and there should be ways to play these games independent of any server/internet-infrastructure behind it, just like it's possible to play old Atari/amiga-games now without the original companies being around anymore.