It's clear to me that iPhone is a compromise device, while iPod Touch isn't. iPhone is essentially iPod Touch plus a bolted-on radio that makes it backward-compatible with existing GSM wireless voice networks. It's like a Mac with one of those MacCharlie things that essentially included an IBM PC.
Two months ago I wondered aloud, Will iPod Touch Get GPS? Now I wonder why everyone is so fascinated by the prospect of 3G (yep, it's faster) and so indifferent to the iPhone's potentially much more disruptive sibling, iPod Touch.
iPod Touch is a pure device—data-only. It's $100 cheaper up front for the customer, and more importantly, doesn't require any expensive, long-term commitment to a wireless carrier—by customers or by Apple. (However, if Apple managed to slip 3G data support into the Touch I'd be thrilled.)
So will iPod Touch get GPS? I'd bet so. Location-based services are set to explode, and Apple is forecast to sell 10x as many iPod Touches as iPhones next year. What else will find its way into the unheralded flagship product of the Touch platform? I can't wait to find out.
Update: As it's been pointed out in the comments, an ala carte wireless data plan would mean that maps for the GPS functionality wouldn't have to be stored on the device. But remember, mapping is only one of many possible location-based services.
Update: Wow, talk about wrong. No updates to the Touch today, and with the iPhone's price drop, the cheapest (8GB) Touch costs the same as the most expensive (16GB) iPhone 3g (ignoring for a moment the $1,440+ you'll pay to AT&T over the course of your mandatory wireless plan). Of course Apple could introduce new iPod Touch models after today (like they might do with the rumored new MacBook Pro models) but it looks like for now Apple has decided to double down on iPhone and leave iPod Touch out in the cold.