A concept mockup of an edge-to-edge iPhone 6 circulates on the web, and it actually looks quite possible to be made. The iPhone 6 concept is exactly the same size as the iPhone 5, but with a 4.5-inch edge-to-edge display with a 754 x 1296 pixel resolution, and that means a 333 ppi. It also have a new Aluminium/Carbon Fiber unibody casing, and is waterproof. The rest of the specs is kinda "dreamy", so I don't bother with them, but as I said, this could actually be a device that Apple could do, don't you think?
To me personally, 4.5-inch is still too small, so I won't buy it anyways.