Knowing Canon means knowing we'll never see a complete uncompromised solution in a single product...at any price.
I agree with Shadowblade that it will be exceedingly disappointing if Canon puts a high dynamic range sensor in the jack-of-all-trades 5D IV, but fails to also do so in the one camera that needs a high dynamic range sensor the most: the 5DS/R.
Like there isn't a compromised solution from any other company. A7s = low-light wonder, contrast detect only, A7r = big megapixel, compressed raws, contrast detect only, A7II = phase detect, lower pixel pitch, not low-light wonder. Canon splitting a 5D lineup is exactly like Sony's lineup, so I don't get the assertion at all, especially in comparison to the other options out there. And I'm not just talking about low ISO DR and the ability to raise shadows, which I do like as I came from Nikon and they did it first (at least before Sony), let's not forget.