I'm not so sure that saturation will injure the genre but I do think that the recent simplification of the gameplay will put off a lot of old timers such as myself. Almost every shooter follows the same silly recipe now and move away from realism and add health regeneration, re spawning enemies and silly weapons designed to be "different".
The way things are going now, I can't see myself playing newer FPS games in a few years, they're taking away some of the core elements, its like taking all racing sims and turning them into arcade racers, fun for those who like arcade gameplay but not so much for those who crave a proper, deep racer imo.