As far as a larger screened iPhone is concerned, we have seen quite a few leaks recently, promoting the idea that the next-gen iPhone will be offered with a 4.7 inch screen. In addition, a phablet-sized model is also likely this year, carrying a 5.5 inch glass. Both sizes could see a jump in pixel density to 441ppi from the 326ppi found currently on the Apple iPhone 5s. The pair of new iPhone models are both said to be employing sapphire glass.
Other speculation about the Apple iPhone 6 states that the 8MP snapper on back will offer OIS. And the aperture will weigh in at f/1.8, which will result in better pictures in low-light conditions than those produced by the camera on the Apple iPhone 5s, which sports an aperture of f/2.2.
As usual with a story of this magnitude, open up the salt shaker and take this story with a grain of the stuff. We have a long way to go until the usual September release of the next-gen Apple iPhone and there will probably be plenty of more leaks ahead.
Alleged prototype of an Apple iPhone 6 case compared to the Apple iPhone 5
1. Note the larger front screen
source: BlingMyThing, 9to5Mac via RedmondPie