Well, the problem is how would you use the hard drive in connection with the ipad? I have the new Seagate wifi drive, but that's designed to be only one way - TO the ipad. That's why I'm using the 2 device process - laptop and drive for storage/editing, and ipad for quick previews. How would you get the photos from your camera onto the hard drive? If you put them onto the ipad first, there's still no way that I know of to then move them from the ipad to the hard drive.
I think the newest model of Seagate GoFlex allows you to upload photos from your device TO the GoFlex unit. Here's the relevant part of the spec sheet:
So, it appears that if you can get your photos into the iPad's Camera Roll, you can move them to the GoFlex unit.
The question then becomes: Can Photos added to the iPad through the Camera Connection Kit be moved to the Camera Roll? IIRC, normally the Camera Roll stores photos taken with the iPad itself or if you save them from a website. New added photos from the CCK are put in a new album separate from the Camera Roll. I do not know of a way to move photos from an Album to the Camera Roll.