According to a small bit of information I received, Nikon may not be ready to launch a new successor to the Nikon D300s, also known as Nikon D400. However, they have a Nikon D7100 in the works. The D7100 would be the first Nikon camera using the same digital sensor as the Sony Alpha 77 (a surprising 24 MP sensor in DX/APS-C format). Most of the existing Nikon D7000 would be kept.
According to this, the Nikon D400 would be using a different sensor of a more specifically Nikon design and of a lower pixel resolution.
No date, no image, though.