DPreview interviewed some Canon managers and DP clearly stated:
“It looks like we’ll have to wait a little longer before we see an EOS R model aimed at sports and action shooters”
And a Canon manager explained why they didn’t make a mirrorless version of the 1DX:
Of course some professional photographers are asking for a mirrorless solution. But as of now, we also see a lot of demand from photographers asking for DSLRs, specifically [because of] the benefits of an OVF. So this time around we decided to go for a DSLR. Of course we understand that there are huge benefits to mirrorless, and we implemented, or combined as much of that [technology] as we could into the [EOS-1D X Mark III].
So it looks like the Sony A9II will not get a competitions from Canon in the near future…