Although 100 units may not seem like a lot, the initial production is a milestone as using sapphire instead of Gorilla Glass does make the manufacture process more complicated but ultimately results in a more durable and scratch resistant screen.
Additionally, Apple's two main sapphire suppliers -- Synopsys and Bern Optics are both working to invest in tools and equipment, another sign that Apple is working to ramp up production even further. Both companies currently provide the sapphire that covers the iPhone's rear-facing camera and the iPhone 5s' Touch ID sensor.
This isn't the first rumor that we have heard of a sapphire display. We could even see it earlier than most expect.