Apple, AT&T Try to Plug iPhone Revenue Gap

That startling high percentage could have been the main reason behind Apple's decision to shift to the phone-subsidy model, offer more choices and build a wider set of carrier partners.

As a result, the percentage of unlocked 3G iPhones could drop to single digits, says Charles Wolf, an analyst with Needham & Co. Wolf owns shares of Apple but Needham does not have an investment banking relationship with the company.

By offering a no-contract iPhone, AT&T has essentially legitimized the philosophy of having an unlocked iPhone, says Gottheil.

"AT&T and Apple have accepted unlocking as a fact of doing business," agrees Gottheil. "With this if people want the equivalent of an unlocked phone and are willing to pay a premium for it, they have an option."

AT&T has said it will offer a no-contract-required iPhone at $599 for the 8GB version and $699 for the 16GB model.

AT&T's no-contract phone is not exactly an unlocked iPhone, says Ken Dulaney, mobile and wireless analyst with industry research firm Gartner. Buyers will still be bound to AT&T's network, he says.

"An unlocked iPhone is one that you buy at the store and can activate on any non-AT&T account," says Dulaney. "The no-contract iPhone still locks into AT&T."

In other words, that gives iPhone buyers three options. They can buy a iPhone with the standard two-year contract from AT&T, or they can get a no-contract phone that can still be used only on an AT&T network but will allow them to avoid early termination fees and give them the option to get another phone or a different network whenever they would like to.