Why do you think this was addressed earlier than the 5d mark III, despite the 5d being released "long" before the 1dx?
The simple answer would be: The 1dx costs more. "Professionals" demand it. etc.
But I don't think there are too many amateurs running around out there with $3000 bodies.
I was relatively unconcerned with the large amount of discontent with the 5d mark iii preformance, personally feeling that the camera fit its role.
I am, however; utterly pissed that Canon chose to overlook the fact that there are thousands of 5d mk3 users out there that have demanded, more or less, that the AF in AI Servo be changed through a simple firmware update, and instead, offer it to the 1dx that has been out for a fraction of the time.
I love Canon, but this really irks me, maybe unjustifiably, but irks me none the less, and where better to rant than cr?