Following the success of the iPhone SE, Apple is thought to be increasing the size of their battery by over 6% in their upcoming phone, the iPhone 7, increasing the battery capacity by another 111 mAh. This comes along with other feature improvements such as a dual camera. The change is not drastic, and may be thwarted by increases in processing power available in the phone, but could yield satisfactory results, especially in tandem with the recent ‘Low Power Mode’ added to the latest version of iOS. The processor chipset has not been revealed, and it’s not yet possible to ascertain whether Apple will once again improve power efficiency or increase performance from this change.
Sources:  http://www.slashgear.com/iphone-7-rumors-new-antenna-dual-cameras-bigger-battery-10435601/