As the world knows, Canon has announced the development of the EOS-1D X Mark III DSLR. While some good information was given by Canon about the upcoming flagship DSLR, not everything about the camera has been made public.
We have been told by multiple sources that there are at least 2 “major” features that are unannounced at this time.
The first one, and probably expected is that the EOS-1D X Mark III will shoot 4K video without a crop and with DPAF.
One source also claims that 5.9K external RAW recording has also been tested in the EOS-1D X Mark III prototypes, but that a decision had not been made at the time of the testing whether or not to include it. We were told a few months ago that 6K was a possibility for the EOS-1D X Mark III.
IBIS hasn't yet been confirmed by any of our sources at this time, but I do believe it's still a possibility. Canon does have to save some surprises for the official announcement in early 2020.
We have been told in the past that the resolution of the sensor would be 20.1mp, and now a second source has made the same claim. Though I haven't been able to confirm it with known sources at this time.