I have a multitude of cameras, and even in mildly difficult environments, I bump up against ALL of my APS-C gear's abilities. At parties, ISO 4000-6400 is common, and even the Pentax K-5 produces images that are pretty smudgy at that level.
My photos get easier and better with every generation. I agree that some time in the future, all sensors will be good enough. That day is not today, though.