As with all things Apple, the day after the iPhone 3GS launched rumors started about its replacement. The replacement has been dubbed the 4th generation iPhone and rumors are swirling anew today.
According to the most recent rumors, the 4th generation iPhone is set to be unveiled on June 22. The evidence for this rumor comes by way of a booking in Apple's name for the conference center where the last iPhone was announced on June 22.
This rumor is unsubstantiated and the booking, if true at all, could be for some unrelated product. However, there have been other reports of a Verizon branded iPhone being used recently so the big day may be coming soon.