I attend a university with about 30,000 undergraduates. From my observation of students and iPods, the iPods are not going anywhere anytime soon. As mentioned before, they simply update the current versions and people buy them again. Now, unless Microsoft comes out with something very identical to the iPods than things might change.
However, cell phones are integrating the functions of a laptop. They already integrated the PDAs but now with faster processors, more memory and hard drive running on Windows Mobile they can run some basic programs like a laptop. Music and navigation are also some bonuses.
If anything, PDAs competition is increasing heavily due to all the new PDA phones also called “smart phones.”