I wonder if they will ever put the GPS in the iPod, or if they consider that a big differentiator for the iPhone.
So, I doubt it, just because it wouldn't add much and would cost significantly more (both in components and battery life).
With this kind of device, you're only online when in wifi, so location-aware services are limited too. i.e. what would you do with the GPS info? Maybe photo tagging?
Using any offline navigator.
I think it is really all about the batter life.
iPod doesn't have 3G, so it's offline outside WiFi range. This means you're either close to WiFi and WiFi-based location works, or you couldn't do much with it anyway.