I think Apple will eventually come out with a device that combines audio, video and pda functionality. The iPod is already headed in that direction and the industry seems to be headed in the direction of two types of convergence devices:
1. Smartphones that combine phone, pda and limited audio/video capability with wifi coming soon
2. Portable In-hand Multi-media Platforms (PIMPS? -
its a joke!) that have larger screens better suited for e-book reading and video playback, pda functionality, audio playback, etc.
The PDA sales data is showing that the day of the typical PDA (primarily for PIM use) is quickly coming to a close. PIM lookup is now easily accomodated with ANY phone and the phone is the preferred location for this info by most users. However, there is and will always be a need for those of us who are looking for document portability (laptop replacement or to compliment our laptop/desktop).
Apple fans don't despair, if and/or when Apple releases such a device it will surely knock your socks off, I'm sure of that.