Depends on what you're looking for in terms of "improvement". For all the Internet chatter about IQ, sensor improvements have been very slow this decade because for still capture sensor tech is quite mature. DxO and DPReview want you to think about nothing but DR, yet the bar for DR was set by the D800 in 2012. People talk a lot about high ISO but there's not 1ev of difference between the best and worst FF sensors currently shipping.My thoughts are consistent with many of you. I've taken my 5D3 all over the world and it's been put through very challenging conditions, taken quite the beating and never failed me. I love my EF L lenses and I am happy with all of them. I didn't make the 5D4 jump (I tried it and returned it), largely because it was not a big enough jump in tech for my needs. The posts are discussing a 1D R and a 5D high megapixel replacement, but I sure hope we see an all around camera that's an improvement over the 5D4 soon, my 5D3 before it goes DNR.
Ironically the area which the press has ignored for the past few years, megapixels, is the area where there's still room for improvement. This is also the area where people seem to complain the most. Witness all the comments from people saying they don't want an 80mp FF RF body from Canon.
The next 5D and/or RF version of the 5D will surely have improved video and AI AF specs. But if you're not going for the high MP RF body that is in the pipeline then don't expect a significant IQ improvement over the 5D4 that you returned. It's state of the art, and that art is now moving at a glacial pace when it comes to still capture.