http://www.huffingtonpost.com/2014/03/18/8gb-iphone-5c_n_4984893.html
Obviously, a metallic smart phone is going to be more durable, but a plastic phone can be a nice secondary communications unit.
The smart phone, is usually a phone first & a computer 2nd.
A nice hybrid is on the way.
http://www.gizmocrazed.com/2013/04/iphone-6-concept-shows-how-wraparound-display-would-look-like/?utm_source=zergnet.com&utm_medium=referral&utm_campaign=zergnet_56349
The handset vs the wrist.
A wearable computer that could also become a phone.
http://wonderfulengineering.com/the-sony-computer-that-you-can-wear-on-your-wrist
A super-plastic or polymer could eventually rival some metallic things.
http://www.materialstoday.com/amorphous/news/plastics-as-strong-as-steel,
http://www.dailytech.com/Transparent+Plastic+Polymer+is+Strong+as+Steel/article9181.htm,
http://www.sciencedaily.com/releases/2007/10/071004143114.htm,
http://www.scientificamerican.com/article/making-plastic-as-strong
http://www.nap.edu/openbook.php?record_id=2307&page=109
