well, what the iPod "wont" become has been covered well, and i agree that a phone tie-in would be rather pointless at this point.
i think the iPod will evolve into the [almost] perfect portable high quality recording device (or at least there will be a version of the iPod in the future for this purpose). this seems like the most logical and usefull direction for the iPod to go, and weve already seen some evidence of this evolution (e.g. the partly implemented record function in service mode, and the suspected audio in/out leads on the dock connector thing). i think the iPod will finally put an end to minidisc players, and their main use as a portable recording device. also, i feel that somewhere down the line this recording iPod could have some useful built in functions in terms of recording; like possible low voltage phantom power from the internal battery, mic level checks, line/mic level switchable decibel settings, and some simple, useful, live waveform processing (like noise reduction, etc...). i would buy something like this in a heartbeat!
EDIT: obviously these functions would have a potentially limited user/buyer base, but i think apple could really win over a ton of minidisc and other audio pros / not-so-pros with something like this as a branch off of a more consumer targeted iPod like the ones we have now.