Recent analyst reports, based off channel checks with suppliers, indicate that Apple would eventually go for a 4.8" panel on its upcoming larger iPhone 6. Concepts iPhone have made another juicy render that depicts how such an iPhone 6 might look like, when housed in a slim body with metal rear, and the speculated 8 MP camera with optical image stabilization on the back. Evidently, Apple will have to find room for the TouchID fingerprint sensor at the front, so the 4.8-incher is unlikely to break records in the phone-to-screen-size ratio department.
The Concept Phone guys also posted a video that arguably shows the iPhone 6 chassis and other parts, allegedly recorded in Apple's assembler factory, which we are embedding below. This one we take with a large grain of salt, though, as it might be anything, and you can't really judge for the phone's screen size from this chassis alone, until you put it next to, say, and iPhone 5s, or another handset, the screen size of which is already known.