According to The Wall Street Journal, Apple will release its next iPhone by the end of September 2011. The new iPhone will be “similar to the current iPhone 4, but thinner and lighter with an improved eight-megapixel camera,” according to the WSJ.

The report also suggests the next iPhone will have a camera upgraded to 8 megapixels, a resolution boost up from the iPhone 4’s 5-megapixel sensor. Other reports say the new iPhone will sport the same powerful A5 processor as the iPad.

Here’s more from WSJ:

A person briefed on Apple’s product plans said the company initially planned to launch its next iPhone this summer as it usually does, but the device wasn’t ready in time.

Two people familiar with the situation cautioned the next iPhone could be delayed further if contract manufacturer Hon Hai Precision Co., which assembles the iPhone for Apple, couldn’t improve its production yield rate.

Boxes of Apple Inc. iPhone 4s are seen on display in Paris last June 2.

Hon Hai Chairman Terry Guo said last month that the yield rate of Apple’s touch-screen devices hasn’t been satisfactory and has hurt its profitability.

“The touch-screen devices are so thin. It’s really difficult to install so many components into the iPhones and iPads,” Mr. Gou said. “We hope to raise the yield rate and volume in the second half, which will help improve our gross margin.”