Daisuke Wakabayashi, for the WSJ:
A hint of troubles at GT came last month, when Apple said it wouldn’t use sapphire screens in its new iPhones, contrary to what many observers expected. Apple added to GT’s financial pressures by not making a final $139 million prepayment loan because GT hadn’t met the technical milestones laid out by the company, the people familiar with the matter said. GT had said earlier that it expected Apple to make that payment by the end of October.
This gives a great insight about why GT filed for bankruptcy a few days ago. This information was completely unexpected for a lot of people, including me, after the news of Apple investing heavily in their sapphire production for the Apple Watch (only rumored at this time) and the iPhone :
“To be clear, we did not see this coming,” Pavel Molchanov, an analyst with Raymond James & Associates, wrote in a note Monday. “We don’t think anyone else did either.”
That's the best explanation for the absence of sapphire screens on the iPhone 6, a feature that was widely expected but not delivered by Apple at it's September press event. But also, it implies some serious threats about the presence of a sapphire screen in an iPhone 6s(?) at all, since it putted GT in a very delicate situation.
But we don't know of what the future is made of.
(Thanks to John Gruber for the link)