Statistically, higher ISO settings are used more frequently these days than lower ISO settings...so it really baffles me that this is such a broad and ubiquitous issue. I am not saying that better low ISO DR is a bad thing, of course it's good...but it is still only one IQ factor out of many. Given how well the D800 has sold, I wouldn't go so far as to say Canon is now playing "catchup" in the low ISO DR arena yet.
Which statistic? Can you point to the result of a scientific study?
And what exactly do you mean by “higher ISO settings”? Higher than 100, 400, 800, 1600…?
I buy into a camera system and the sensor is just one part of the system, but I would love to have the low iso DR of the D800 in my 5DIII.
It’s the one area Canon is really outperformed by just about all other manufacturers. I think they should address that for the next generation and they probably will.
All manufacturers are playing catchup in some way, because none of them are the best at everything.
High ISO...I'd call that ISO 800 or above. ISO 100, 200, and 400 I consider low ISO, although ISO 400 is kind of in the middle there, and others might have a different opinion.
I don't have a specific study. It's a simple observation, however on that I have been making over the last four years or so. (FYI, I've moderated photo.stackexchange.com since 2010, and have encountered and chatted with quite a number of photographers over the last four years from a wide range of photographic endeavors.) How many white Canon lenses do you see at pretty much every sporting event around the globe? Hundreds to thousands at each and every event. Canon dominates sports, hands down, no question. They really dominate action, not just sports. I spend a lot of time out in nature, and meet a fair number of nature photographers. The very vast majority of the people I've met out in the wilderness, including both wildlife and bird photographers as well as landscape photographers, overwhelmingly have Canon equipment. Canon 1D IV, Canon 5D III, and Canon 1D X are becoming almost ubiquitous in the wildlife and bird world. Canon great white lenses, 300s, 500s, and 600s, are extremely common (particularly the 500 Mark Is...lot of wildlifers and birders use that lens, guess it's at a sweet spot of weight and cost). I've met a few who have Nikon equipment, two of whom use D800's for bird photography. I know of one (now a good friend) who uses Pentax and Nikon. I also know and have encountered/chatted with a decent number of wedding & portrait photographers. Most use the Canon 5D II. A few still use the 5DC (they don't seem to care about resolution). Some use the 5D III (and all of the 5D line wedding photographers had one consistent complaint before the 5D III: Sucky AF.) I know of several wedding photographers who use Nikon and other brands (some have gone to mirrorless as of late, with a variety of brands.) I know two wedding and portrait photographers who use Nikon exclusively. One uses a D800 and D3, the other uses a D7000, with a D800 planned for very soon. I would say that Nikon seems to have a growing following in the strait portraiture arena...not so much for DR, but for the sheer amount of detail the D800 or D600 bring to the table...seems that ridiculous, razor-sharp detail that brings out every single pore is really "in" right now, and there is no question that the D800 offers that in spades.
So, sorry, I don't have an official study for you, but it really isn't a difficult observation to make. Just look around. It's a very well-educated guess. The number of cameras and lenses that you can spot in the world that say "Canon" on them vastly outnumber any other brand. Of those, the biggest group that uses the most cohesive set of camera features are the action shooters. Sports/Olympics, Wildlife, Birds...and you can throw in car racing, air shows (know a few guys who do this, damn good at it too), kayaking, boat racing, pretty much anything you could remotely call a sport, or has moving subjects...the camera is going to be at a higher ISO setting, and is probably a 5D III or a 1D X. The next two biggest groups would be Wedding & Portrait, and Landscapes. Not sure which is bigger...seems pretty evenly split here in Colorado, but if you hit larger metropolitan areas, I would make the educated guess that Wedding and Portrait photographers would end up significantly out-pacing the Landscape photographers (and I mean real landscape photographers...I know more people than I can count who use entry level cameras, Canon, Nikon, Sony, Pentax, everything...and call themselves landscape photographers, but their work wouldn't land on anyones walls (no offense to anyone like this, but)...blown clouds, random people in the frame, lack of interesting composition, effectively point-and-shoot mountain peaks and a few scattered rocks or stubby evergreen trees here and there, never any post processing, thrown up on Imgur, PhotoBucket, or Facebook.)
I honestly don't have all that much knowledge about studio photographers. I can't really say how big a customer segment studio photographers might be for Canon...but I guess big enough for them to create the 1Ds line in the past. What I DO know about studio photography, it seems to lean medium format (or maybe Leica S-system) a lot more than it leans Canon, Nikon or Sony. Phase One also seems to be the brand I hear about most from the studio photogs I do know or have crossed paths with.