There was an article about why September 30th. It said that that date could be the date of win they announce a Verizon iPhone, but I highly doubt that. Here's the article if you wanna take a look at it
http://www.gadgetsdna.com/iphone-5-coming-in-october-rumors/4821/
http://www.gadgetsdna.com/iphone-5-coming-in-october-rumors/4821/