Apple is said to be internally testing a new beta of iOS 6.1 that is expected to be the golden master build, suggesting the software is nearly ready to be released to the public. From Apple Insider:

Citing a "reliable source," iFun reported on Friday (translation) that the fifth beta of iOS 6.1 is about to be released to developers. The software is said to have gone through "extensive internal testing," and if all goes well it will be the golden master of the software.

The software is expected to be released to developers either on Friday or potentially on Monday.

Final iOS 6.1 beta being prepped for developers