Canon and Nikon are both expected to release their respective top-of-the-line camera - EOS-1D X Mk II and D5 some time in late 2015 or early 2016. I have written about the upcoming EOS-1D X Mk II but so far there is no real specific information about its capabilities.
Nikon Rumors claims the new Nikon D5 will have 4K video, 20MP full frame sensor, native ISO of 102,400, 15 fps and 173 AF points. The first three features sound plausible but the last two sound like a wish list. I will be very surprised Canon will let Nikon trump their Mk II camera.