There are some improvements in iOS7 that should improve battery life, though it's hard to say by how much compared to decreases from introducing more multi-task

There are some improvements in iOS7 that should improve battery life, though it's hard to say by how much compared to decreases from introducing more multi-tasking. This includes batching LTE network access from multiple apps. Though we can't know the full impact of the new APIs until apps start taking advantage of them, many who used beta 4 and 5 claimed better battery life than on iOS 6. For me being able to very quickly turn off wifi, bluetooth, and lower brightness via the control panel has probably made the biggest positive difference. I'm more likely to leave bluetooth off most of the time for instance since I know it takes less than a second to turn it back on.