According to latest rumors, the Canon EOS-1D X Mark II will be replaced by Canon EOS-1D X Mark III in late 2019, release date around Q4 of 2019.
The new Canon EOS-1D X Mark III will have updated DPAF, and a new sensor tech. Other specs is not available yet. The source also said that we may see EOS 5D Mark V in 2020.
via: CR