Apple has been working hard to fix a battery issue which they apparently failed to fix with iOS 5.0.1. So maybe Apple is planning to fix it once and for all with iOS 5.1.
Apple is also planning to add more features to Siri with this iOS release, including commands to toggle Bluetooth and WiFi connections.
So if you are an iOS developer download iOS 5.1 Beta from here
Developers who have gotten their hands on this release have found hints of a new iPad model within the code. The model iPad 2,4 suggests a new version of the iPad 2. It wouldn't be the iPad 3 which would be referenced as iPad 3,x but it could be referring to a 3G model of the iPad 2 for Sprint.
We will keep our eyes on the iOS 5.1 releases as it evolves, and be sure to update our readers if it fixes the illusive battery issues.
source - 9to5Mac