What I think would be cool, is not a new iPod, but as someone else said, a superdock. My vision of the product would be a dock that holds 2 iPods, and has additional controls, whatever may be needed like fade, pitch, etc. Or, maybe the "pro" iPod would be mostly self contained, but have a dock for a second "regular" iPod, either for more tracks, or for more control on crossfades etc. I think it would be pretty cool, especially for weddings, birthday parties, etc. That way those types of DJs can have more pop tunes to please more people, and hopefully land more gigs.
Another thought, why not make the pro iPod slightly bigger, and incorporate regular laptop HDs, or even full size drives, so you could put 250GB of music, so uncompressed audio would be very feasable. Laptop drives are up to 80gb, and im sure they are working on getting them bigger.