The second half of 2015 will be decision time for Canon. They want to introduced the EOS-1D X Mk II, EOS-5D Mk IV and EOS-6D Mk II, three full frame cameras that need a replacement soon.
The EOS-6D Mk II will still be the least expensive full frame camera in Canon's line up and may go slightly upmarket with a new sensor, more AF points and higher native ISO with better weather sealing, higher quality material, powered by the DIGIC 6 processor(s).
The EOS-5D Mk IV may come with a low 20MP sensor but will be equipped with a new AF system, perhaps sharing it with the new EOS-1D X Mk II. It will be powered by new processors, most probably dual DIGIC 6+ but DIGIC 7 is also possible but unlikely for now. It will boast superior ISO performance and 4K video is still a possibility.
The EOS-1D X Mk II will be a Nikon D5 slayer. It will have a new mid 20MP sensor, state of the art AF system accompanied by unmatched dynamic range and native ISO performance. Multiple new processors will power the camera to a slightly higher frame rate, perhaps up to 14 fps without the need to lockup the mirror. It will have improved ergonomics and a slight weight and shape change due to improved material.
Everything is still very fluid in the Canon's decision making process. Nothing has been firmed up yet and I suspect once Nikon announce their D5 later this year, we will know more about Canon's plans. Test cameras are out in the wild with selected contract photographers and I hope to get more information as the summer and autumn months roll around. Keep checking back for the latest development. I am still on my road trip in the Canadian Rockies doing some travel photography. Visit my website MichaelDanielHo.com to see photos from my past trips and you can follow my travel on Twitter and Facebook.