Next-generation iPhones likely to focus on internal improvements.
iPhone 6 May See Only Modest Battery Capacity Boost as Apple Pursues Ultra-Slim Designs
Chinese media sources claim the 4.7-inch version of the iPhone 6 will ship with a battery between 1,800 and 1,900 mAh, while the 5.5-inch iPhone 6 will include a 2,500 mAh battery. Though larger than the 1,560 mAh battery in the iPhone 5s, these modest capacity increases place Apple behind competitors with similar sized handsets, and leave some wondering if Apple is keeping the battery too small in order to design an ultra-slim device. The larger screens on the iPhone 6 will naturally create more volume for larger batteries while maintaining a slim profile, but the displays themselves are likely to require increased battery to support the higher resolutions.
Of course, these rumored battery capacities for the iPhone provide only part of the equation, with Apple's tight software-hardware integration also contributing to overall battery life. It is also possible that real-world battery life may be better than these speculated hardware specs imply due to underlying performance improvements added to iOS 8.
Apple is expected to unveil the iPhone 6 during a September media event. The company may debut both a 4.7-inch and a 5.5-inch version that could feature a faster A8 processor, an upgraded Touch ID scanner and an improved camera with some form of image stabilization.