A Verizon iPhone: A wash

Sprint Nextel, T-Mobile USA: Unless Sprint Nextel (NYSE:S) also gets a CDMA version of the iPhone, it is likely to lose out, along with T-Mobile. Bajarin said that Sprint and T-Mobile tend to attract different kinds of customers than Verizon or AT&T, especially those who are more cost-conscious. They will likely stick with Sprint or T-Mobile for the value, he said.

"I think it's a bit neutral for T-Mobile and Sprint," Jackson said. "Defections that would have happened have already happened."

Android: Gartenberg said that a Verizon iPhone might blunt Android "a little bit," but he said it is wrong to assume that the smartphone market is a zero-sum game. "Both are going to coexist in the marketplace," he said. Additionally, due to the number of vendors and carriers supporting Android, and the variety of price points for Android phones, the platform is likely going to survive a Verizon iPhone.

Android grew from a 3.9 percent smartphone market share in 2009 to a projected 17.7 percent share in 2010, according to Gartner. "I can't imagine you get a Verizon iPhone, and [Android] maintains that growth," Bajarin said. "It will maintain a lot of momentum. Maybe not maintain that absolutely explosive growth."  

Windows Phone 7: AT&T has pledged to be the premier carrier partner for Windows Phone 7, and a Verizon iPhone could give AT&T the opportunity to put its money where its mouth is. "AT&T is very aware that they need more than one very strong leg to stand on," Entner said. "They know they need to be capable and successful with multiple smartphone platforms. They will certainly give the others quite a bit of attention."

At the same time, as Burden notes, the iPhone is a known quantity and Windows Phone has a lot of ground to make up, especially in terms of consumer consciousness. A Verizon iPhone could suck oxygen in the debate away from the platform.

Research In Motion/BlackBerry: Research In Motion (NASDAQ:RIMM) is already tussling with Apple, and a Verizon iPhone could up the tension. Verizon has long been one of RIM's strongest supporters, and like the other handset makers would take a hit in marketing support. However, analysts noted, RIM has a large and loyal enterprise base that could mitigate any loss.

A Verizon iPhone: A wash