That's assuming the technology being developed is to store an existing credit card on your phone - isn't it more likely that Apple will try to make a play that

That's assuming the technology being developed is to store an existing credit card on your phone - isn't it more likely that Apple will try to make a play that involves your app store payment setup? Presumably, the implementation would be to expose your payment setup as a "virtual" Amex on your iPhone, but without making you a direct customer of Amex, but clearing the transaction through the Amex network.