It isn’t exactly clear what kind of impact this will have with developers. What will be interesting is to see if developers who may have already moved on to other projects will return. There have been a number of documented cases where bugs in games have been reported, but nothing was ever done to fix the game.
It is difficult to say how much this is going to matter in the future. We would like to think that many games will get patches to correct serious problems now that there is no cost. We will just have to wait and see how motivated developers are to fix these issues, rather than just sweeping them under the rug. It is currently unknown how or if this rule might apply to the Xbox One platform.