A contributor has had this to say about the AA filter rumor and that it's unlikely Canon will remove it from the 1Ds Mark IV.
MF camera makers deleted AA filters primarily for reasons of cost, not image quality, as aliasing is very destructive. Yes, they do use software to “correct” this, but it does a terrible job. It's an insoluble problem, because it's a “many to one” issue for the software.
Large AA filters are very expensive to manufacture, particularly at MF quantities. A Pentax representative even stated flat out that cost was the sole reason they didn't include one in the 645D.
Canon will delete the AA filter once resolutions get high enough that diffraction is the limiting factor.
The ‘next 1Ds' was delayed for some bigger jumps in technology and to hold it's ‘top camera' spot for longer. DigicV will allow for handling of binning, better video and ‘software removal' of the need for an AA filter at 35+MP. The camera might not ship until later next year.
I asked around to find out if software could correct what the lack of an AA filter could bring about. Most notably; moire. The general consensous was it was possible. A regular contributor pointed out medium format cameras do not have an AA filter and combat moire in software (thanks Kurtis).
For those that don't know, the lack of an AA filter would produce sharper images right at the sensor. However, Canon has a lot of lenses that would need to be upgraded to resolve a sharper 35+ mp sensor.