The DigiTimes which is one of the most relaible sources for information about ios rumours claims, that Pegatron Technology who is a Chinese manufacturer has received a request to develop the iphone 5 for a September launch. This rumour could have some truth value, because this is the company that currently makes OEM parts for the iphone 4s and the new ipad. 

This report seems to appear to further validate the release dates of either September or October.  If there is any truth in this rumour which there is a good possibility of,  it would make it impossible to get the iphone ready in time for the Worldwide Developers Conference (WWDC) event in June.