Apple is gearing up for production of the next iteration of its iPhone line, and has begun ordering parts from its supply chain, according to a detailed report from The Wall Street Journal. The newspaper offered details on when it will ship (September) the form factor (thinner than the iPhone 4), the wireless chips used (Qualcomm), and an improved camera on the device (8 megapixels).

Not all of these bullet points are new — informed speculation that Apple would ship the iPhone 5 (or 4S) in September began in earnest more than three months ago — but they do come with The Journal’s reputation for properly sourced material and information vetting.

The report also included a caveat that a September launch could be delayed if Hon Hai Precision was unable to improve yield during its manufacturing of the iPhone. If true, it would suggest that Apple is serious about being able to meet demand when the device launches, rather than playing catchup for weeks or months afterwards.

To that effect, The Journal noted that Hon Hai Chairman Terry Guo said in June that, “The touch-screen devices are so thin. It’s really difficult to install so many components into the iPhones and iPads. We hope to raise the yield rate and volume in the second half, which will help improve our gross margin.”

Be that as it may, Apple reportedly has internal goals of producing 25 million of its new iPhones by the end of calendar 2011.

The article quoted an unnamed person in Apple’s supply chain who said, “Apple’s sales estimates of the new iPhone are quite aggressive. It told us to prepare to help the company meet its goal of 25 million units by the end of the year. The initial production volume will be a few million units.”

One other note, in the This Is My Next article about a new, pro version of the iPad that Apple will also reportedly be releasing in September, there was a mention of why rumors have been mixed about the form factor of the next iPhone.

At one point, it was thought that Apple would be only slightly modifying the design of the iPhone and call it something like the iPhone 4S, while other reports said that Apple’s top leadership (i.e. CEO Steve Jobs) wanted to put the design of the iPhone 4 behind them, and not keep it around for three generations like it did with the original iPhone.

Today’s report from The Journal said that Apple had come up with a new design that was similar to the iPhone 4, but both thinner and lighter.

Joshua Topolsky reported that because the iPhone 5 is thinner and lighter than the iPhone 4, Apple has been testing the internal components inside iPhone 4 cases, thus sparking some of the conflicting reports.