According to said sources, factories will begin iPhone 5 production in July at the earliest with a release slated for September. Apple's next-generation smartphone will reportedly have a faster processor but otherwise have a similar appearance to the iPhone 4. There was no mention of the rumored larger screen or 8MP camera from Sony.
This September shipping date rumor contradicts earlier ones that the iPhone 5 would only begin production in that month. As TUAW notes, the Reuters report would make more sense given that Apple is apparently focusing WWDC solely on software this year to show the future of Mac OS X and iOS. The company could hold off introducing its next-generation iPhone 5 until fall when iOS 5 should be ready.
It remains to be seen if the iPhone 5 -- or whatever Apple ends up calling it -- will be released on AT&T and Verizon simultaneously. This will be the first new iPhone launch since the exclusivity contract with the former carrier expired.