Apple recently filed a rather interesting patent with theUSPTO, the US patent agency. In this one, the Apple models a flexible iphone in the true sense of the term, since it can be bent in any direction.
Although it is unlikely that the Cupertino company will ever offer a smartphone of this type, this patent can be used to improve its resistance. If future iPhones gain in flexibility, they will no longer deform (read: Is the iPhone 6 Plus really easy to fold?) And the components will be less sensitive to shocks.
It therefore remains fairly plausible that Apple decides to barter thealuminum current of its phones against a more flexible material such as the silicone. Of course, the Californian finish will always be there. However, the subject can be controversial: would a more resistant iPhone made of silicone be as successful as a more fragile iPhone made of aluminum?