I also disagree with most people who want a thicker iPhone with better battery life. Apple's quest for thinner devices is not vain.
Most of us live in developed countries, where we can afford to come home everyday and charge our phones. We also have free access to power outlets pretty much wherever we go. Need to charge it midday because you forgot to charge it overnight? What a hard life. We just don't need a bigger battery, unless we go hiking for a week in which case we'd certainly be ok with it, or.. get a beautiful Smart Battery Case. People who'd really need an improved battery life are people who can't afford an iPhone in the first place, like some islanders, or any remote areas without electricity.
Apple's thinking way ahead of the iPhone 7, they know exactly the research that's happening in terms of nanotechnology. As components get smaller and require less power, it makes sense to have thinner devices, until a breakthrough happens. And it'll happen:
http://phys.org/news/2016-03-silicon-devices-looms-big-discovery.html
"Imagine having a phone that you don't have to recharge but once a month"