The 5D Mark III has a 6 FPS continuous rate. It's not unreasonable to expect the Mark IV to max out at 7 or 8 FPS. However, there are situations in which I don't need a full 8 FPS. The Mark III has a high speed mode (6 FPS) and a low speed mode (3 FPS), but often, I find 3 FPS to be a bit too slow for things like the first kiss, while 6 FPS fills the buffer a little too quickly. It would be great if I could dial in the speed setting that best suited my needs, especially if the Mark IV sees a bump in its maximum rate.
1D series has had this for some time, I guess I never noticed it was missing with the 5D3, because I my default setting has always been to set my 1D to 6FPS anyway.. so never needed to adjust the 5D3. Don't have my 5D3 in front of me so can;t even say for sure if he's right.