We definitely see improved detail resolution...
But, it might be said that the megapixel count specification itself can EXAGGERATE the impression of improved resolution. After all...
- 12 Mpixel 5Dc camera is 4368 x 2912
- 50 Mpixel 5DS camera is 8688 x 5792
...but the pixel count in a SINGLE AXIS is only 2x ! Only 2x the possible detail resolution in a single axis (Nyquist Limit says 4343 vs. 2183 line-pairs) while requiring 4x the data storage requirement.
And then you have the fact that very few photos are enlarged over 13x19", and this would result in 458 pixels/inch from the 5DS sensor -- which the human eye cannot even detect!
Unless you print at 19" x 29", you are not using the 300ppi potential from 8688 pixels, so you might as well continue to shoot with a Canon 5DII which imposes far less data storage demands yet fully satisfies the need for about 300ppi on a 13x19" print.
We marvel at the improved noise characteristics of the new 5DIV...imagine if we continued to shoot at a 5Dc resolution sensor, yet applied the same silicon manufacturing techology and the same noise processing as used today in the 5DIV...just how marvelously free of noise the images would be when the sensor has 2.3x the area (signal generating area) per pixel.
And then we view them on monitors that only have 2M-4M pixel count, or with projectors that have 2M pixel count (that's what most of us can afford to buy reasonably), so even the 5Dc resolution 12Mpixel is wasted for the most part...just think how few images even MAKE IT onto paper!