Sapphire is supposedly 3x more scratch resistant than Gorilla Glass and other such scratch-resistant materials, and in about 3 years, it should get about 3 times more popular than it is today, thanks to adoption in smartphones.
Right now it’s mainly used in LED’s, but Apple has already started using it since last year on the iPhone’s camera, and this year in their Touch ID, on the home button, because having an unscratchable surface there is pretty important, in order to scan your fingerprint properly.
Apple is not going to be the only manufacturer who will use sapphire, and even though it’s still like 10x more expensive right now compared to Gorilla Glass, while being 3x more resistant against scratches, I think we’ll continue to see it increasingly more on top of cameras, buttons, and even as displays, as economies of scale make it cheap enough to be used as touchscreens.
Eventually we may even see companies make full phones out of a sapphire unibody, but don’t expect that to happen in the next 2 years, unless it’s cutting a lot more on other specs, to compensate for how expensive the phone’s body will be. I could see Apple wanting to put it in an iPhone 7, though (that’s after iPhone 6 and 6S), so if other OEM’s want to beat Apple to market with a full sapphire phone, they might want to plan to beat them to it by late 2016 – unless they want to be seen as copycats, if they also do it after them in 2017.