The hacker known as "Chronic," who is a member of the iOS jailbreaking community, revealed the news in a post to his official blog on Tuesday, citing a "very solid source." He said the golden master of iOS 5.1 recently completed a three-week "vigorous quality assurance phase," and should be released in the coming days.
The software update is expected to have support for the Japanese language with Siri, Apple's voice control personal assistant software currently found in the iPhone 4S. The GM build of iOS 5.1 is said to be known as "9B176."
In addition, iOS 5.1 is said to include two unknown new features that have not yet been leaked to the public. The update is also said to feature an easier method of accessing the camera from the lock screen, something that was leaked in a screenshot of an alleged pre-GM build of iOS 5.1 last month.
iOS 5.1 has reportedly been tested internally at Apple, as well as with various carriers and partners. Because of this, the build may already be in the hands of some unauthorized people, but because the firmware is not being signed on external servers, it cannot be installed on any unauthorized iOS devices.
Apple began seeding beta releases of iOS 5.1 to developers last November. A second beta arrived in December, followed by a third beta in January, but since then there have not been any new betas issued to developers.
It's likely that iOS 5.1 will be discussed or even released at Apple's media event on Wednesday in San Francisco, where the company is expected to unveil its third-generation iPad. The event will kick off at 10 a.m. Pacific, 1 p.m. Eastern.