Why wouldnt it be? As long as the final version of iOS7 isnt released, the phone can be downgraded to whatever version Apple is currently signing (which is iOS 6.1.3/6.1.4)
Why wouldnt it be? As long as the final version of iOS7 isnt released, the phone can be downgraded to whatever version Apple is currently signing (which is iOS 6.1.3/6.1.4)