A funny thing has happened, Since Canon policy always was that:
the bigger the sensor the more of a pro you are.
We see such a tendency, that canon mainly values the size of the sensor, and since a camera doesn't use Full frame, no matter how advanced its controls and features are, it is never going to be considered as a serious camera.
So... this unwillingly puts them into a trap. 645D camera's sensor is bigger than a full frame, and many Canon Pro's as taught by canon see it as a more professional camera than their 1ds's.
The most pro, Canon users that I know of, looking at 645d with big eyes, and they are kind of dreaming about it.

so Canon made "Pentax medium format" a favor.
however.. It might be so, that canon themselves are noticing it, and will start working on their own medium format.. I believe, such rumors already exists.. and I believe, if, they will make one, they'll make it really good.
however2 Canon doesn't not have any lenses for medium format yet..
Well pentax should manufacture more 645d and of course work on a second generation one, to quicker attract those who, have $ and will..
what are your ideas?