There are professionals who spend all day talking into a device to be typed up later, by themselves or others. Doctors. Lawyers. Journalists. Professors. Students in professional, even undergraduate schools could record class lectures, to be typed up later. Such a device would even be quickly adopted by Indie Film makers and video journalists, instead of Radio mics. Voice and location recording is important.
I just don't know if the ipod chipset has the built in ability to encode, this might have to be designed into a widget that plugs into firewire (perhaps with a choice of mic in, or built in mics), extending the length of the iPod.
I don't think apple would be likely to change the form factor of the iPod in order to add recording capabilities, but they might allow a well designed third party add on to tap into new software capabilities. I don't know if the interior electronics would need to be changed or not, but again, that could be built into any plug in widget. Even if the unit did not compress to MP3 on the fly (It could store 80 hours and record 10 hours before recharging if so) a 4.6 gig iPod could record AIFF stereo for 2 hours at a time before recharge, and hold 8 hours.
Right now, the best competition to the iPod, Archos Recorder 20, (yes it has firewire too, -when- it comes out, just not the elegant interface or design) can record. Don't underestimate the attractiveness of a recording feature, I have a friend who almost decided to stay with his wintel boxes, and get an Archos (Archos Jukebox by the way, is Mac compatible as well). I think this needs to be enabled in any iPod upgrades. The iPod is good for other data other than Music MP3s.