You don't have to wonder how Canon will respond to Nikon's Z-series mirrorless cameras (and by extension Sony) -- many of the details now appear to be out in the open. Nokishita and Canon Rumors have posted leaked details of the EOS R, a 30.3-megapixel full-frame cam that would primarily compete with the Nikon Z6 and Sony's A7 III. The design would thrive on low-light photography with a wide ISO 100 to 40,000 normal sensitivity (up to ISO 102,400) and the company's familiar dual-pixel autofocusing. Those aren't exceptional specs given the increasingly competitive full-frame mirrorless space, but there would be a few twists that might give it an edge over its rivals.
Via: Canon Rumors (1), (2)
Source: Nokishita (translated)