Just as with the iPhone 3G launch, AT&T has now posted a blackout period for its employees during June 2010. The blackout period ensures that no employee takes any time off during the specific period.
The blackout date for June 2010 is believed to be for the new iPhone launch this summer 2010. The new iPhone 4G or iPhone HD (what ever you want to call it) is expected to debut on June 22, 2010, which is an odd day for an iPhone launch being a Tuesday.
In any case, the new device is expected some time in June 2010. In previous years, iPhone launches occurred on Friday, such as the Original iPhone on June 29 2007, the iPhone 3G on July 11 2008 and the recent iPhone 3GS on June 19 2009.