A Mexican carrier executive of Telcel announced last week that the iPhone 4 will go on sale on Friday August 27, but he also spoke about a hardware revision will be coming at the end of September, without reception issues, according to Canal-Mix.com via Macrumors.com
The carrier executive explained that Apple will be shipping a hardware revision for the iPhone 4 at the end of September, the same time the company plans to stop giving out free cases. Telcel said in the press release [Translated] that the updated iPhone 4 hardware will be available on September 30, 2010.
Apple originally announced on July 16 that they will be giving customers a free case of their choice, or a refund, to fix the antenna issue with the device. The free case program will run between July 23, 2010 - September 30, 2010, for all customers with an iPhone 4.
It's not uncommon for a manufacturer to release a hardware refresh on a faulty product partway through its lifecycle, like when Apple released an updated bootrom for the iPhone 3GS in mid-September 2009, just months after it was originally released. The updated bootrom made it harder for hackers to jailbreak and unlock the phone.