DoW3 will do alright on release but I don't see it doing much for the genre in the long run. RTS isn't a ded genre yet but it does appear to be in a downward spiral with lack of appealing titles leading to less interest in the genre, in turn leading to less financial incentive for development of new releases. Seems like most releases are either remakes/'HD editions' of classic titles or 2nd-tier titles that offer an interest gimmick but lack polish.
People hold up SC2 as the pinnacle of RTS, as if to argue that if that game can't succeed, no game ever will. That's just not true, SC2 is far from a perfect game. For all its simplicity it still has a steep learning curve and despite the shiny graphics it retains an ugly and extremely 'gamey' aesthetic. From a single player perspective it has become excessively campy and suffers from Blizzard's tendency to rehash the same themes and plot lines.
So I think there is still potential for a successful RTS if it can get that winning combination of accessibility, innovation, polish and marketing, although of course that's much easier said than done. For CoH3, that would mean focusing more on its strengths, learning from past mistakes instead of repeating them, driving sales through good marketing (ideally timed closely with the next big WW2 movie/TV series), then supporting the game through thoughtful patches and worthwhile DLC.
The thing about blizzard is that they are the kings of updating and adding new and meaningful content to their games. While some people might complain, the quality of their patching is miles ahead of whatever relic puts out.
Sure, relic is better than before at the frequency of patching (coh1 days) but their patches always feel 60%-80% done. There's always something missing, wrong or just plain old fucked up. It may seem like a worthy effort to you newer players but us older guys are pretty worn out by it.