Pundits quickly connected that detail with a rumor recently reported in the Nikkei:
Suppliers of LCD panels for Apple's new iPhone will ramp up production soon, in line with a timetable for a worldwide launch as early as September. The new phone, expected to be called the iPhone 6, will likely be offered in 4.7- and 5.5-inch versions, both of which are larger than the current generation's 4-inch screen.
There's no indication as to the source of this rumor, so I would not take it too seriously. Also, Apple is know for their secrecy, so if this screen really were intended for the next iPhone I don't think JDI would have been allowed to announce it.
Remember, the Retina Display for the iPad wasn't announced by Samsung; it leaked from a parts supplier. That is how I expect to first hear about the new larger iPhone screens - assuming they exist.
While I expect Apple to eventually release a larger iPhone, all of the rumors I am hearing right now sound an awful lot like the rumors circulating around this time last year. A lot of people expected a new and larger iPhone last September, but it didn't happen. Instead we got a couple new iPhones with 4" screens.
Without a solid leak which proves the existence of the larger screen, I think it is safe to assume that many pundits will be disappointed when the new iPhone is unveiled in the Fall.