Imaging Resource published their interview with Kenji Tanaka (Senior General Manager Digital Imaging Group, Sony Corp.) and it is their understanding that Sony will no longer provide other manufacturers with some of their sensors/technologies:
As you know well, our key driver is the image sensor, and we already invested a lot of money for the image sensor development. And the sensor is a custom [design, meaning that] only Sony can use these sensors, and our strength is our in-house technology. So I invested in that and we will keep investing in the in-house technology like image sensors.
Ed. note from Dave Etchells: This was new information for me; as far as I'd been aware, Sony's camera division would get access to the latest sensor designs as soon as they came through the design and production cycle, while other companies could buy the same sensor a year later. While this might once have been the case, it appears that Sony currently reserves some level of their sensor technology exclusively for us in their own cameras.
This could be one of the reasons why Nikon has not released a new camera in the past 15 months (I do not count the D3400 and D5600).
Update: shortly after my post the interview was removed but you can still find it on Google cache.