...Given that the 5DIII has sold better than the D800/E, please explain the flaws in Canon's strategy...
The fact that the 22 MP 5DIII has outsold the 36 MP D800/E and a7R supports the idea that the market has not demanded high MP...therefore, Canon sees no need to respond, quickly or otherwise.
I don't think Canon's strategy was wrong at the time. . .I don't think Canon could have produced the D800 two years ago at the D800 price period, which has nothing to do with whether or not the 5DIII was the right product for Canon to make...
...If it arrives around 3-4 years after the D800, which is similar to Canon's pro product cycle length, then I would think Canon is reacting to the D800. If a high MP comes 5 or more years later (or never), then Canon decided that the high MP market was not worth its while.
Both Canon and Nikon responded to their customers. Nikon customers complained about Nikon's low resolution and Nikon overcompensated.
Canon's 5DII customers complained about the weak autofocus and were convinced Canon would just keep piling on pixels at the expense of noise and high ISO performance. (Go back and read some of the forum posts before Canon released the 5DIII.
Canon overcompensated by putting in an incredible autofocus, keeping the resolution almost the same and improving ISO performance.
Fortunately for Canon, their market research turned out to be more accurate than Nikon's. In fact, it was sufficiently accurate that they could charge a premium for the 5DIII over the D800 and still outsell Nikon by a wide margin.
I do think you will see a high megapixel body from Canon. It's just going to be in an APS-C format and called 7DII. (24mp scales out to more than 61mp in full frame). Why? Because a high megapixel 7DII plays to the format's strengths; it has a market; and it fits in with Canon's two-body strategy by nicely complementing Canon's full frame options.