Preview at WWDC likely in June, followed by September launch.
Apple Releases iOS 6.1.1 for iPhone 4S Devices, Fixes 3G Issues
A beta of iOS 6.1.1 was released in the middle of last week carrying a build number of 10B311 -- it's likely the upgrade released today was an urgent bug fix and the prior iOS 6.1.1 beta sent to developers will become iOS 6.1.2.
About iOS 6.1.1 Software UpdateThanks to @AppleNicholas for the screenshot
This update fixes an issue that could impact cellular performance and reliability for iPhone 4S.