WiFi meets the G family
The Seattle Times serves up an insightful layman's overview of the interaction between the 802.11 market and the billing and data services plans of the cellular carriers. They bother to explain the acronyms, which I usually don't.
Single billing may be the 'good enough' outcome that wins. I'm sticking with my forecast that public WiFi is going to end up a combination of a free location amenity and a rather low-priced uplift to cellular or ISP subscriptions. The deeper integration of roaming voice from cellular to WiFi, and data in the reverse direction, is rather problematic and the article describes some of the reasons. Add in a few more details like handset energy budget and BOM cost, and the potential QoS problems for VoIP on loaded public APs. [Those acronyms you will have to look up yourself.] We may get there, but it's a bit further out.