Thom Hogan says in his 2011 predictions
Nikon committed to using only Nikon-design sensors. That doesn't mean that the sensors don't have elements from other makers in them or that they stopped using Sony as a supplier, only that Nikon's sensors appear to now be 100% exclusive to Nikon. When you compare a Nikon DX 14mp or 16mp camera to a competitor's, any difference in image quality is now completely engineered by Nikon. The results so far look very promising, so Nikon is on to something.
Saying that certainly does not imply that Nikon no longer use Sony to fab at least some of their sensors.
I am pretty sure I have read somewhere (and with some degree of authority) that the D3100 was probably not Sony made but the D7000 definitely had a variant of Sony's new 16Mp CMOS sensor in A55 and A580. The same applied to Pentax's new K5. Sony have the capacity (and adding to that capacity). You cannot at the drop of a hat transfer large quantities of sensor production to other sources. It taken years to increase capacity on this scale. This is not like developing a new source for the D3s. I am sure that Sony's sensor division will be as happy to listen to Nikon and Pentax's requirements as to those articulated by their own Alpha division. Sony's sensor division have probably signed strong confidentiality agreements with Pentax and Nikon and may know how to make better sensors than those specified by the Alpha division, but can't spill the beans. That is why the K5 may have a better DR than both the D7000 and A55 with the same basic sensor.
