According to CR, the upcoming Canon EOS-1D X Mark III now in testing by a small number of photographers and/or engineers. The Canon EOS-1D X Mark II was announced on February 1st, 2016, now it is three years old.
The announcement for Canon EOS-1D X Mark III is expected in next year around CP+ Show 2020. As we already know this camera hasn’t shows up in the upcoming Canon camera codes, so don’t expect imminent announcement for 1D X Mark III. And specs, price is not available yet. Stay tuned.