That's not the final production model. Most likely there will be little change, but surprises are always possible.
It's not competing against other Canon models. It's competing against Sony's and Nikon's offerings.
Maybe, but it's a bit simplistic to only consider the sensor resolution and DR. And the 5DS/5DS R is aimed at studio use, not landscape use in particular.
Canon have apparently redesigned part of the camera (e.g. mirror mechanism) to have improved camera shake performance. Maybe Sony have learned (at the expense of customer experience) that higher resolution and (in their case 'shutter shock') camera shake performance both need to be addressed at the same time. For studio use, which is the main market that the 5DS and 5DS R seems to focus on, tethering performance is also very important. Accurate color reproduction is another area that Canon say to have paid attention to. Seamless integration of the redesigned lenses, with Autofocus and in some cases Image stabilization, is bound to be better with Canon bodies for Canon lenses. Just to name a few other points of consideration.
The main issue with the 11.3 stop DR of many Canon sensors is/was that the pattern noise made lifting the shadow detail (which has few photons to work with) a less than optimal avenue, but if pattern noise can be controlled better, then good noise reduction in postprocessing becomes very much more usable. For JPEG shooters, there is already an option to shoot HDR bracketed exposures to a single JPEG output. A similar thing has become available for the masses in Lightroom for Raws. This can produce
much better shadows than is possible with a single Sony sensor shot, because photon shot noise will be
much lower, and Signal to Noise Ratio
much higher. De-ghosting methods are getting better, and subject motion in bracketed series of shots is becoming less of an issue.
So Canon chooses a different approach than Sony does. Fine, that will give us a choice.
Cheers,
Bart