I agree with you that a carrier is needed for this to take off. I disagree with your assessment of Verizon as "forward-thinking". This is the carrier that disabled the ability to load mp3 files to the original Motorola Razr, even though the phone was fully capable of supporting USB syncing. Verizon wouldn't carry phones with Wifi radios until the success of such phones on alternate carriers (the iPhone and BlackBerry, in particular) forced it to catch up to the market. I see nothing to indicate that Verizon has changed their thinking - they still like to charge for every little thing as much as possible.
I think T-Mobile is the most likely to experiment with Ubuntu as an alternate OS to offer customers. They've been willing to try new operating systems in the past, so there's a track record already in place to support the idea.
Keep Up with TechRepublic