A report from Mexican publication CanalMX includes comments from Marco Quatorze, director of Value Added Services at Telcel who is the Mexican carrier of the iPhone and began offering the iPhone 4 last Friday alongside Czech Republic, Greece, Poland, Portugal, and Slovakia.
In his comments Quatorze says that as of September 30th Apple will begin shipping revised hardware with the antenna issues resolved. The end of September coincides with when Apple's case program ends which has in the past led to speculation of a hardware revision.
The comments by Quatorze discovered by Mac Rumors shouldn't be given too much credence, it is unlikely that Apple has passed on such information to carriers.