Last week, I went out on a limb and pre-ordered the 24 megapixel Nikon Z6, which should ship on November 30. It is a bit of a flyer, but assuming my instincts are correct, the camera will replace my second body, the Nikon D750.
Currently, I have two cameras, one a Nikon D810 and the other a D750. They are my first and second bodies respectively. I use the D810 almost exclusively for jobs, and the D750 serves as a second backup body in case of failure, and a personal project camera, too. I intend to upgrade both cameras over the next year and a half, and I definitely want to move towards mirrorless.