There are plenty of other issues associated with sapphire. It's heavier than Gorilla Glass and the material remains less transparent than glass, meaning it would be more difficult to see the screen unless manufacturers add a special coating to increase transparency. (Even then, it still wouldn't be as good as glass.) Additionally, each representative I talked to confirmed that while sapphire is durable, it certainly isn't unbreakable. In fact, the larger the display is, the more brittle it becomes; "The sapphire is too hard to withstand bending," said a representative of a top-tier phone maker who also asked to remain anonymous. "It's easier to break during drop tests when the size of sapphire increases."
Another representative replied, "In a cost-benefit analysis, I doubt [using sapphire] makes sense, unless there is some perceived marketing advantage." Despite the potential downfalls of using such a material, that's exactly what Apple would be gunning for by using the display in the iPhone: marketing power. Sapphire's got a solid reputation; if the new iPhone features the same material used in premium watches, necklaces and earrings, and the company can throw it in without raising the price to consumers, Apple has a great new way to distinguish itself from the competition.