On the site where they announce Adobe CS5 is a technology demo of the mercury playback engine that will be implemented in premiere cs5. According to the video, it will be able to playback several of the newer formats, including the Canon DSLR files, in real-time. It will use CPU and GPU together to achieve this.

Go to Adobe Creative Suite 5 Launch (http://cs5launch.adobe.com/) and click on the mercury engine video! Bit about canon DSLR is around 04:20.