In a note to clients — as reported by “AppleInsider” (www.appleinsider.com) — Canaccord Genuity analyst Michael Walkley says that for the first time since it launched last October, the iPhone 4S has been replaced as the top selling smartphone in the U.S. — by the new Samsung Galaxy S III, which took the top spot in the month of August.

Samsung’s lead is expected to be short-lived, however, as Apple is expected to unveil its next-generation iPhone next week at the Sept. 12 “It’s Almost Here” event. Walkley said in a note to investors on Tuesday that his checks with U.S. carriers found that iPhone sales have been soft ahead of the launch of Apple’s next iPhone, allowing Samsung’s Galaxy S III to take the top spot.