It may also be that Canon is using the low-end (cheap) model as a test to see what sort of market demand this announcement creates.
By making people send the camera in to them for this "firmware" upgrade, they know exactly how many people are interested. If they allowed the firmware to be downloaded then the numbers would be approximate.
The only people who will send the camera in are they ones that really want this AF since they have to give up the camera for some period of time.
Possibly also they can get some stats from the cameras how it was used, this is speculation on my part.