This rumor doesn’t seem especially legitimate, but Marco Quatorze, the Mexican carrier Telcel’s “Director of Value Added Services”, told the tech website CanalMX that Apple would be shipping updated iPhone 4 units on September 30th.
The new version supposedly has a fix for the antenna issue, but it is unknown if this would be exclusive to Telcel, or a global update. He mentions that early adopters would recieve units that still have the issue, but would be given the option to upgrade to the newer model without extending their contract.
However, Quatorze also said that after September 30—the date Jobs promised an update on the antenna issue and the date that the free case program expires—Apple will begin supplying revised iPhone 4 devices that “do not have the reception malfunction.”
I’m pretty skeptical on this one, considering the source.