iMore is reporting that Apple will announce the new iPhone and an iPad Mini on September 12, for release on the 21st.
The relatively earlier-than-expected announcement would make some sense; Apple repeatedly cited next-generation iPhone rumors as being the reason iPhone 4S sales fell short last quarter, so the sooner a new product hits shelves the better. The basics are a stretched-out 4-inch screen and a smaller dock connector. But details about leaked components have ranged from smuggled phones to leaked parts to fully assembled units made from those parts. If those hold up, the next iPhone has been making the rounds for a while now.