Given the target market, the price and the fact that their reputation in the professional market rides on this camera, is it any wonder that Canon wants to make sure the thing is as close to perfect as possible before releasing it?
If they think this, they must be really desperate - engineering is always a compromise between dev time and product lifecycle, thus making "near perfection" an idea for geeks, not for a commercial company. It's much more likely that they found flaws (f8 af?) they couldn't get away with given the competition, so rather than "near perfection" its more like "good enough".
1.) By improving 1DX to not leave the impression that 5D3 is abandoned.
Abandoned customers will abandon the brand.
Are you suggesting that Canon would be well-advised not to put any significant last-minute improvement in the 1dx, because it may make the 5d3 look bad? Geez, this is the way of technology - and Canon will hardly stop development because some 5d3 users are a bit touchy when they hear "Nikon" and could not stand internal Canon competition, too. Didn't tons of 5d3 threads establish that the 5d3 is a great body at any price and nothing else matters, esp. not other alternatives :-o ?
I had in mind that they could try NOT to put a "last-minute improvement" (significant or not) but to include a "big" improvement which they have behind the closed doors - something like a BSI sensor - they have the technology, put the link bellow in the Google Translate to see:http://egami.blog.so-net.ne.jp/2012-01-23
...also have a look here:http://photorumors.com/2012/01/23/sony-develops-next-generation-back-illuminated-cmos-sensor-with-rgbw-coding-and-hdr-movie-function-canon-files-a-patent-for-a-large-bsi-sensor/
For an expensive product with a long life cycle like 5D3/1DX the early adopters are one of the most valuable assets of a company. It they will feel betrayed then they will betray - a damage which is very hard to repair after. I know this from many years of experience.
Having a camera being twice as expensive and two or even three times better it is understandable. But having a camera ten times better just because they wanted to fool the early adopters and enthusiasts with 5DMk3 - this will backfire. Too few will think that they had a stiff competition from Nikon/Sony and they needed to throw everything against them. The ones who purcased an comparatively over-priced 5D3 will feel cheated and next time who will dare to commit?
OTOH, from my small experience, as I stated elsewhere and it seems that I'm not alone, they now try to overcome some design issues and to improve to the max the firmware (this includes also end-user features like black AF thing but also the internal processing engines like ADC / noise handling etc.). The risk is way to big (imho) to redesign hardware now.
But I think that's critical for them to crowdsource their problems even in the form of "rumors" (this is one the best ways to keep the brand goodwill untouched) because more eyeballs will see better and perhaps a solution will appear from "nowhere" (if it didn't appeared already