VoIP functionality could be delivered through the device's already-revealed WiFi capability. A rumored add-on attachment that fits into a dock on the Zune would, it is believed, be able to hold a mic necessary for these calls.
What's seems to be a bit more challenging to me would be how to fit VoIP functionality into a non-clamshell design.
No clamshell- no foldover to go back and forth from the viewer to an onscreen dialpad.
One way to circumvent this would be an add-on keyboard that could, when accessed via an extra "phone" (or probably cooler-named) prompt in the Zune onscreen menu I am showing you, would call up an in-viewer indicator that would display the numbers as they are dialed.
Rather than a separate display, I'd like to see this onscreen phone number indicator-or, if necessary dialpad-shrinkable to a small portion of the active player window.
I'd also like to see an onscreen buddy list and address book functionality in the Zune. Also accessible via the add-on keyboard, this buddy list would also shrink to a smaller window in the Zune player.
The reason I like the smaller window for the buddy list and addy book is that a Zune user could still be watching their video or listening to their music as they summon their pals via phone or IM.
And then, what about some sort of real-time sharing capability that will allow you to share the music or video you are partaking of with your friends?
If Zune offers all these features (literally and figuratively) out of the box while iPod is still bound to the synching cradle without any realistic communications capability, iPod's world may be rocked.
And not in the music sense of the term.