In efforts to further improve the iPhones, maufacurers are putting together a metallic glass to replace the current models. The metallic part would prevent the phone from cracking or breaking as easily, while the glass components still maintain the strength.
This used to be a very expensive process for manufacturers, making it difficult to produce high volume of these products. Thanks to recent technological advances, they have found a process that costs about the same as it does to produce plastic. Although there are no finalized plans yet, the idea is being entertained and may be a feature of the phone in the future making it much more durable and  without ridiculous prices.