If Nikon doesn't get their act together on DX...

But that's hardly the point. If DX/APS-C is dead, Nikon and Canon have only themselves to blame for their mindless iteration over the past five years. But Canon is more than just a camera company and will survive to fight another day. Nikon is only a camera company, to all intents and purposes. As for a D400, 20MP would have been sufficient, and Expeed 3 could have handled it. And there's no way a mirrorless system will use DX and 35mm "natively" - that would mean F-mount.

--
Jim