I can't seem to find any reference to High-bandwidth Digital Content Protection or HDCP support in the new iMacs on the Apple website. In fact, I can't find HDCP mentioned anywhere on the site at all.
That is a real disappointment. If the new iMacs truly do not support HDCP, that means they may essentially already be obsolete if you're interested in the next generation movie formats. Even if you were to add an HD DVD or Blu-ray drive to the iMac, even if full-fledged HD DVD or Blu-ray playback software existed on the Mac, and even if the OS (ie. Leopard) supported all the formats' features, the new aluminum iMac still would not be able to play back these movies at full resolution, if at all.
Thanks to readers that have pointed me to the Ars article that states that HDCP is in fact supported in the new iMacs. If true, perhaps Apple has not yet mentioned it simply because they have not yet implemented it on the software side, and may activate it later in an OS upgrade.