It's a fact that Apple is investing heavily in supplies of sapphire crystal, including building their own manufacturing facility in Arizona that's expected to come online this month. It's unknown, however, exactly what this material will be used for. Virtually indestructible, the material is currently used to protect the camera lens and the Touch ID from scratching in the iPhone 5s. So what else will Apple be using it for? According to comments made Wednesday by the CEO of a company called Canonical that had to scrap plans for making a smartphone, Apple has bought up the "entire three-year supply" of the same sapphire crystal display they had been planning to use for their 4.5-inch device. The comments, which were reported by GigaOm, diverge somewhat from the most recent rumor out of the Far East that Apple would use Corning's Gorilla Glass for the 4.7-inch iPhone 6 and sapphire crystal for an "experimental" 5.5-inch "phablet."
I'm guessing that Apple itself doesn't yet know which material will be used in the iPhone 6. It's clear that they see sapphire crystal as the future, given their investment in this material. But it likely depends on the availability of the material, how much it will end up costing to use it in a display, and how much they themselves will be able to produce. You have to admit, though, that a sapphire crystal display would be an appealing feature: no more shattered glass, no more scratches.
While the comments about a "three-year supply" make it sound like a lot of material, that was for a new phone from a relatively unknown company. It's probably a fraction of what Apple needs for their various purposes.
So here's hoping that sapphire crystal will be a feature of the new phone. A helpful post on GottaBeMobile summarizes what we know about the features of the forthcoming iPhone 6. Regarding the release date, the site says the obvious: the earliest we'll see it will be this summer, and the latest will be this fall. I think September is most likely. The phone will probably use the same anodized aluminum as the iPhone 5s. Most everyone is expecting a larger display of 4.5 to 5 inches with higher resolution, and possibly thinner bezels such that the overall size of the phone, while larger, won't increase proportionate to the 5s. The device itself may also be thinner than the iPhone 5s.
There are also increasing rumors that the new phone will use the A8 processor that Apple is working on. It's amazing that while the rest of the industry is struggling to match Apple's 64-bit A7 processor used in current devices, the company is already forging ahead with an even more powerful processor. The new phone may also come with iOS 8. Rumors say this next version won't seem much different from iOS 7, which saw a radical overhaul, but is expected to have a greater focus on health and fitness, including a new app some are calling Healthbook.
Some market analysts think it's urgent that Apple come out with this new phone because they're falling behind. A recent ad from Samsung makes fun of the smaller, lower-resolution display of the iPhone compared to the Galaxy Note 3.