As already mentioned, there's an enormous difference between having a controller as a peripheral and having it as the default input method. PCs have been capable of taking any controller of any kind for many years now -- how's that working out? Anything but M/KB controls are still niche with no sign of that changing. For that matter, how is that Move thing working out for the PS3? Lots of Move games on the shelves? Experimental input methods are not something one can easily impress upon the marketplace. Making something "technically capable" of using a certain controller is actually the easy part; the hard part is popularizing it.
Further, my list was hardly exhaustive. How about the 3DS? The PSP? The iPhone? Android? Kinect? All of these devices have their own strengths and weaknesses, very few have the same technical capacities and very few have the same input methods as a default.
Many of the people who want a "one console future" are, in my experience, people who prefer the "traditional" form of gaming represented by a standard home console and a standard game pad, and want all these new types of gaming (iOS, DS, Wii, Kinect, etc) to either conform or go away.