I posted a very similar comment on the thread about reaction to the firmed-up specs of the 5D3. (I too begged for two more stops of DR--fat chance.) To me the lack of dynamic range in the 5d2 is its most glaring deficiency-- and the 5D2 is probably one of Canon's better performers in this regard. And yet there seems to be very limited concern about dynamic range among the users of this forum. I think I am the 393rd reader of your post, and the first to make a response.
For me DR is a constant problem--much more so than autofocus or high ISO performance. Any time there is a horizon in my composition it's a pretty good bet that something is either going to be blown out or blocked up. As you say, there are many occasions where neutral density filters, AEB/HDR, even a tripod, are not practical because of subject movement, location, etc. What's really disturbing is to compare my current efforts to some of my 40-year-old prints from 35 mm film. I don't expect two stops in the new 5D, but if there isn't at least one real stop, I'll spend my photographic budget on lenses. The 24L TS-E is looking mighty tasty.
I was going to open a thread on this subject myself, but I'm new to this forum and before flogging what I assumed was a thoroughly dead horse, I did a forum search. Until you started this thread I found incidental snippets, but not one thread devoted specifically to DR issues.
You've raised the question in relation the next 5D; if it isn't hijacking the thread I'd like to broaden the discussion to the whole issue of DR in digital photography. Is this a historico-political problem? Are we in this pickle because we haven't made our needs clear to the manufacturers? There are ten demands for better high ISO performance, more resolution, or faster autofocus for every complaint about limited dynamic range. We've seen major advances in all those other areas. If Canon thought we were really bothered by the limited DR of their products would we see that two-stop DR improvement in the 5d4?
Maybe it's a specialized problem, primarily of concern to landscape photographers? I can see where DR might not be as big an issue for studio photographers, where the photographer and not nature is in charge of the light as well as the composition. Do wildlife shooters miss the dynamic range of film?
Or is this a technical problem? Digital photography has made amazing strides over film in areas like resolution, maybe even color rendition. Modern high ISO performance makes 20th century efforts to "push" film look like something out of the bronze age. On the other hand, perhaps DR is particularly daunting challenge for CMOS technology. Would you have to give up something else to realize a significant gain in DR? Then too, is there a technical reason why Canon lags behind other manufacturers in this area?
All of this leads back to your question of whether the next few generations of digital cameras hold any significant promise for improvement in DR. Do we just have to get in Canon's face, or are we condemned to wait for an as-yet undreamt-of technology? It would be interesting to hear on these issues from people knowledgeable about the historic and technical aspects of photography.