The Canon 5DS & the 5DS R were fantastic high-resolution cameras who deserve a mirrorless successor. The EOS R5 is a 45-megapixel performance monster, however rumors indicate that there may be an even higher megapixel count sensor undergoing real-world testing as we speak.
The rumored R5S may have a 90-megapixel sensor and a higher resolution EVF than the R5. Rumors indicate that s small group of photographers may already be testing the R5S in the wild.
Let us wait for additional information as it becomes available.