More rumor stuff... from the Canon camp in UK referencing the D400:
"... the 7D2 is being actively positioned against an upcoming D400 from Nikon and will be announced around the same time... the 7D Mk2 is going to be firmly aimed at the sports and nature market, with a lot of features based on feedback from 'pro' users. The 10 fps rate is seen as an important feature, along with many features derived from 1DX developments, particularly AF and lower light performance. Sensor size would be advertised as 21MP, but faster and less noisy than the 7D (25MP was apparently seen as not offering enough image quality)."
The pressure is ON Mr. Nikon... and I'm sure that you will deliver. :)
On a similar topic as this relates to possible capabilities debated here over and over... I tried the Nikon V1 today with 70-200 f2.8 (540mm equiv) and also with the TC17 (900MM equiv)... Works fine with the first lens, but it accentuates that the one thing which DSLR's do well is focus at higher f-stops on fast glass whereas the mirror-less does not. Focus hunts terribly at f4.8 for the combo, and stopping it down any makes it useless. In other words, the future for sports is the D400. It's also capable of processing very high frame rate (60 frames per second at full 10MP in RAW) using the high setting for the electronic shutter... not saying that this is appropriate for people looking at the D400, but only that 10FPS at 24MP is a breeze to process from a data flow standpoint. Of course the buffer fills up fast with the 9meg RAW/NEF files, but not until I squeeze off 30 of them. All that with a $300 kit. So the frontier is fast autofocus not processing speed for frame rate, as of course with enough juice, even larger then DX mechanical shutters are capable of 10FPS on full frame cameras.