I believe that Nikon is facing a dilema.
After the issues that the EOS-1Ds Mark II had with the autofocusing system (that hit the heard of Canon sports fortress together with the D3s / D3s) Canon set to create a truly next generation autofocus system, and they succeed. They also set to fight with the high iso performance of the D3s. Nikon started this generation from a relaxed position, it was a mistake. Logic will tell you that they could have added a better focusing system (D7100) to the body, but that will move the D600 successor directly into the D800 territory. Nikon needs to improve the focusing system of the D4, to make it competive with Canon. After that they will be able to retro fit the D800 /D4 auto focus system down the line.
In my case I don't do sports (but I do dance) and the current D600 AFS works for me.
Do they solve the aperture control during video issue on the D610?
Best regards,
J. Duncan