Apple’s worldwide single-carrier exclusivity model for each nation is seen as fleeting, as a new report suggests the iPhone could be available for carriers other than AT&T in the U.S. within a year.

In his latest note to investors, Gene Munster, senior research analyst with Piper Jaffray, takes on 14 “unanswered questions” that surround Apple. They address the company’s financial guidance, the iPhone, iTunes, iPods and Apple retail stores. One prediction suggests Apple would add new iPhone carriers in the U.S. with the debut of a new product in the summer of 2010.

“For various reasons the company moved from an exclusive relationship with French wireless carrier Orange to a multi-carrier model,” Munster said. “In France, the company now enjoys dramatically higher market share (in the 40 percent range vs. about 15 percent in ROW) than in countries with exclusive carrier agreements (such as AT&T in the U.S. where the iPhone has market share in the mid-teens). We believe Apple is seeing the increased unit sell-through more than offset the slightly (~10 percent) deteriorated economics per unit involved in non-exclusive agreements.”

This as the iPhone 3GS has had an outstanding launch, with Apple having trouble keeping the device in stock. The Piper Jaffray report states that the new iteration of the iPhone “seems to have exceeded Apple’s internal expectations.” Additionally, Munster does not believe Apple will offer another model below the $99 iPhone 3G with a cheap, mass-market device. Noting that $10 basic phone models dominate markets like India, he said Apple would likely pass on that segment of the market.

The Piper Jaffray analyst is not alone in believing the iPhone could jump ship next year, as others believe Apple is looking to Verizon as a possible alternative. Even Denny Strigle, Verizon’s president, has been complimentary of the iPhone this year, as his company is rumored to be fast-tracking its new 4G network for launch by early 2010. AT&T, meanwhile, is said to be continuing its negotiations with Apple, in an attempt to keep the iPhone exclusive through 2011. While customers have been extremely satisfied with Apple’s phone and have embraced it, many U.S. customers have been disappointed with the AT&T network.