The Canon EOS-1D X Mark III will be the upcoming Canon Flagship full frame DSLR camera to be announced next. According to CR, the field test for this camera now already started by a small group of photographers.
The EOS-1D X Mark II was announced in February 1, 2016. So we may not see 1D X Mark III coming soon in 2019. The expected announcement date is around CP+ Show 2020 next year. Specs of Canon EOS-1D X Mark III is not available yet.