According to Gizmodo, a source inside Apple said that it is quote "highly probable" that the iPhone 2.0 Golden Master will hit this friday.
This would match the alleged early release date of the App Store (rumored to be June 27th).
The iPhone 2.0 operating system Golden Master will follow the release of build 345, which has seen the activation of two code-signing and encryption features not previously available.
The source also noted that the date is tentative, saying "this is the plan". A highly convenient statement if the said source turns out to be wrong.