Official Canon press release
here.
Youtube video
here.
Lunar check the above video at 6:24. The new batteries are backward/forward compatible with the old 1Dx battery.
Only two limitations are if you use the "old" battery in the "new" camera the FPS drops from 14 to 12 fps. And two, to fully charge the "new" batteries you need to use the "new" charger.
24 of more MP would have been great but Canon and Nikon will slooooooooooooooowly dribble out features every two years to keep people buying/upgrading.
Features that stand out for me:
- f/8 support on ALL AF points.
- Build in GPS.
- DPAF. Dual Pixel Autofocus.
- 4k60p video.
The Nikon D500 shoots up to 29m59s @ 4k30p but does it in 10, 3-minute, chunks. It will be interesting to see if the 1Dxii does the same thing. Also I think Nikon will now have to fix the D5 to shoot more than 3m of 4K video. They better firmware upgrade the D5 before it ships.
Now the only two "important" unknown variables left between the 1Dxii and D5 are: 1) the high ISO performance; and 2) how well the new AF systems actually work.