I'm looking forward to Fuel Cell technology. Insiders expect it to start making its way into consumer notebook computers and mobile phones in 2-3 years.
A hydrogen cell inside will power your laptop for 20-30 hours, and can be recharged INSTANTLY by clipping a cannister onto the fuel port. These cannisters will hold hundreds of charges worth of hydrogen and be available VERY cheaply from your local corner store, service station or supermarket. No fossil fuels, and no emmissions other than water vapour.
So, yes, they are definitely working on new options and new technologies as far as battery power goes.
As for using AA batteries on the iPod, forget it. Even the best quality AA batteries would only be able to power it for 10 hours use. This would be expensive and bad for the environment (think of how hazardous all those thrown away batteries really are).
Still, I wouldn't mind seeing a clip-on extended battery for the iPod ... maybe Belkin can whip one up! :-)