Apple will release not one, but two new iPhone models this September, Deutsche Bank analyst Chris Whitmore wrote in a note to investors on Monday. The Cupertino-based tech giant has a new iPhone 5 model lined up to replace the current iPhone 4, but it also has the rumored “iPhone 4S” in the works — a supposed modest upgrade that will maintain the same physical design as the current iPhone model. The 4S model, Whitmore believes, will launch as a $349 prepaid phone with a data plan that works much like the iPad Wi-Fi + 3G; users will be able to choose from multiple data plans and purchase them on a monthly basis without being locked into a contract. “With Nokia and RIMM struggling, the time is right for Apple to aggressively penetrate the mid range smart-phone market (i.e. $300-500 category) to dramatically expand its [total addressable market] and market share,” Whitemore wrote.