Not a particularly well kept secret, Nikon have officially announced the development of the D5.
There are no details as such just this announcement, including a new wireless transmitter and a Speedlight:
Development of Digital SLR Camera Nikon D5
London, UK, 18th November 2015: Nikon Corporation is pleased to announce that it is developing the D5 digital SLR camera, which represents the next generation of professional Nikon FX-format models.
The new Wireless Transmitter WT-6 and Speedlight SB-5000, which will be positioned at the top of Nikon’s Speedlight lineup, are also being developed.
Through the combination of this next-generation professional camera offering an even higher level of performance, these advanced accessories and the rich lineup of existing NIKKOR lenses, Nikon is pursuing further possibilities for imaging expression.
* Details including release date and suggested retail price for this product have not yet been determined.