Gizmodo has it on good authority that June 9 is the date of 3G iPhone's release. After WWDC, Apple will begin selling the new iPhone to U.S. customers. Europe will not wait too long this time around. Apple may also try to sell iPhones in a different way. We don't know how different it is going to be but fixed prices may be a thing of the past for iPhones. Wireless carriers with the exclusive contracts can offer cheaper iPhones to switchers and other incentives used to great effect with other phone models can now be used to the iPhone.
Update: Looks like Gizmodo's authority was indeed someone of authority. The Apple 3G iPhone is here.