During a reqular earnings call, Sharp's president Takashi Okuda revealed that iPhone 5 display is finished and shipments will roll out this month. Sharp is one of the three suppliers of new screens for Apple and this statement from Sharp will certainly add more fire to the earlier September 12th announcement rumor.
In addition to Sharp, LG and Japan Display Inc. are companies that behind a new panel that, according to rumors, should end up to be 4-inch in size and quite thinner due to the use of so-called in-cell panels that integrate touch sensors in the actual LCD rather than in a separate layer.
If all goes well, Apple might truly announce the new iPhone 5 at the rumored September 12th event, and September 21st has popped up as a rumored street release date.
Of course, these are still rumors, and most importantly, these are Apple related rumors so a teaspoon of salt is more than recommended.