I tried out the 70-300 DO amongst others before buying my 70-300L. The L achieved most of the goals of the DO, so I think that if the technology is to be used for a zoom, it would make more sense for a superzoom, as dgatwood suggests. That would allow Canon to respond to the longer superzooms available from third parties, and achieve an f/5.6 aperture at maximum zoom for maximum compatibility with AF in camera bodies.