According to latest rumors Canon will a new RF mount mirrorless version of the EOS-1D X Mark III DSLR in 2021. It is expected to arrive in the second half of 2021, just before the Tokyo Olympics 2021 in Summer. This will be a flagship Canon mirrorless body and named as “Canon EOS-R1“.

Although we do not know the features of this new model yet, we can say that it will not use the same sensor as the 1D X Mark III. As a result we expect the Canon EOS-R1 to use a brand new sensor. Other than that it will be a RF mount mirrorless version of the EOS-1D X Mark III DSLR.
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https://www.dailycameranews.com/2020/09/canon-eos-r1camera-to-be-announced-in-2021/