Looking into the wiki article on Compact Flash the main historic benefits of CF compared to other mediums (SD, SDHC, MemoryStick etc); capacity and read/write speeds, have all but disappeared. The only remaining one that I can think of is that, with CF, the controller is on the card itself.
There is the argument that with the 7D being a professional grade camera, and Canon's pro cameras going before it having used CF, that you wouldn't want to annoy those who'd invested in your marque and the more expensive, >300x speed CF cards. In addition to this many pros carry 2 camera bodies, often using their previous one as a back-up should the need arise (e.g. dead battery grip), and the requirement of carrying 2 different types of media takes up valuable bag/pocket space.
IMHO the future is probably SDHC/SDXC cards with built in wifi...