AT&T's lies about iPhone tethering "coming soon" might have persuaded some customers to hold on, but now the alternative options are becoming too easy (and cheap) to resist. Particularly in regard to mobile hotspots:
AT&T's delay on tethering has created a serious market for their competitors. The needs of those millions of iPhone customers AT&T is collecting profits from are not going to be ignored by other companies, just because AT&T decides to.
AT&T's attitude seemed to be that those customers would just suffer along without tethering until AT&T got around to forcing tiered pricing on them. It didn't work. Technology, this time in the way of mobile hot spots, keeps moving forward even if AT&T isn't ready for it.
Offering reasonable tethering rates would have been a good way to keep iPhone customers happy, and away from competitors. Too late. Once someone switches from AT&T service for their iPhone, you think they're going to sign up for AT&T service on their iPad?
Randall Stephenson's prediction that the iPad was a "wi-fi" device might come true in an unexpected way. It will be a wi-fi device that people use with Verizon or Sprint mobile hotspots. The above post points out what I've said before: AT&T's gouging of Apple fans has led to a lot of us thinking that a cheap alternative no-contract phone and a good wi-fi connection (mobile hotspot) is better than AT&T iPhone service.
By the time AT&T offers iPhone tethering they might be forced to give it away for free in a desperate attempt to keep hold of valuable iPhone customers. AT&T might finally learn that being a dumb pipe is better than being a pipe no one wants to use anymore. But by then it might be too late even for free.