A new business strategic for the iPhone?

During an interview, Apple's chief operational officer Tim Cook stated that the company was "not married" to an exclusive-carrier business model for the iPhone.
This is the first time that an executive does not shut the door for non-subscription models, and this single sentence makes us hope for an unlocked version of the iPhone in the future.
But, married or not, Apple is bound by contracts to the operators, and except if they have foreseen a special clause, such a development of the market would probably make these operators less willing to renew their (exclusive) contracts with Apple.