Let's see. Sony states that they can produce 30000 36MP sensors a month and Nikon says they can produce 30000 D800 units a month. Just a strange coincidence?
So far as I know, Nikon has been using Sony for their DSLR sensors for a number of generations, including the D700. Nikon does not have a fab, so they do not have the technical means to manufacture their own sensors. I don't remember reading that Nikon engineers have said Sony does not manufacture the sensor, but I seem to remember reading that they said that the camera uses a Nikon designed sensor.
I understand that the Nikon 1 sensor is built by Aptina; and we know that they don't have anything in their lineup that is larger that 16MP.