How long will iPods stick?

I have been thinking about new technologies, trends, what's cool, what works, what sticks, and what translates to business. One cool new (as in this century) technology is the iPod. What I wonder is how long iPods will stick. I look at it's predecessor, the Walkman. Walkman's hit the market at about the same time I graduated from collage. If I remember correctly it was as hot and hip as an iPod is now. I remember buying one, using it to to go jogging or to lay out in my back yard. I thought of myself as hip when I had my Walkman. Within a few years I stopped using it. It wasn't the lack of music or having to carry around tapes since I mostly listened to the radio. It was just no longer hip and I really no longer felt the need to have music with my all the time. According to a recent article in the Economist (12/20 pg 41) interest in music increases in your teens and peeks in your early 20's. This could also be why I lost interest in my Walkman. But it doesn't answer why everyone lost interest in their Walkman. You might say that iPods are more versatile since you can download songs and radio shows onto it; But back in the 80's we thought our Walkman was versatile. In 20 years the iPod may look simplistic for it's lack of versatility based on technology and trends we have not considered today. I wonder how many more years until iPod looses it's cool?