Preview at WWDC likely in June, followed by September launch.
Apple Confirms Battery Life Issues With iOS 5, Software Update Coming
A small number of customers have reported lower than expected battery life on iOS 5 devices. We have found a few bugs that are affecting battery life and we will release a software update to address those in a few weeks.”There have been a litany of complaints about iPhone 4S and iOS 5 battery life ever since their release last month. A number of solutions have been proposed by the community for this problem, including turning off Time Zone detection, Bluetooth and others.
Apple has already seeded developers with a 5.0.1 beta that is said to address the issue.