I began my camera journey, the 2nd one anyway, with the Canon 5DM2, then 5DM3, the 5DM4, then R5. With each new (to me) model I gave my wife the older model so she and I could shoot together. We have then sold off the surplus lenses and bodies. So for this, most likely final body upgrade, I sold the 5DM3, and kept the M4. This is the first body I have kept though which I feel I would still like to use, since it has the touch screen controls. The others, once I had touch screen, were too frustrating to go back to.
I have never had a crop sensor body, but I do use the crop mode on the R5, so I would question the need to keep a crop body unless there was a second person involved, since the R5 has the best of both worlds. I have gone to using the R5 exclusively for my daily driver, but have used 2 bodies for video, so having the second camera on hand is useful to some ends.