I just updated from the 7DII to the 5DIV. So far I am happy with the update. The 10 vs 7 FPS turned out not to be a drag. But the IQ of the 5DIV with the 100-400L II, even after appropriate cropping, beats the 7DII in my experience. I have been using the new camera every day the last two weeks, mostly for birds, so it is a real life experience.
While the 7DII is a great camera, I never liked its IQ when used with the Canon 1.4x III TC. On the 5DIV there is really very very low IQ degradation with that TC and the 100-400L II. The "croppability" of that sensor with the 100-400 II is just amazing!