The fifth generation iOS, the operating system for Apple Inc. (NASDAQ: AAPL) mobile devices, was released in October last year alongside the iPhone 4S. Also made available for older devices, iOS 5 promised 200 new features. iOS 5 introduced the iCloud service, revamped notifications, improvements to native apps such as the Camera, new applications like Reminders, Newsstand, and iMessage.

The new iPad, which boasts of a high-resolution "retina" display and support for the 4G LTE data networks (a first for an Apple mobile device), was released in March this year. But the tablet only had iOS 5.1, which had incremental updates to iOS 5. iOS 5.1 features include support for Siri in Japanese, a camera shortcut now visible in the Lock Screen and a fix to the battery life issues affecting the iPhone.

The iPhone 5, which is expected to be launched in June (same month as first generation iPhone until iPhone 4) or October (exactly a year after iPhone 4S was unveiled, will likely be the flagship device for iOS 6. According to unconfirmed reports, the iPhone 5 will have a 4.6-inch screen and a retina display. Aside from a bigger screen size, it is expected to have radical design changes. Like the iPad 3, it will also have 4G LTE support and a quad-core graphics processor.

Apple has traditionally unleashed new version of its mobile operating system at its annual Apple Worldwide Developers Conference (WWDC). This year's conference is rumored to be held June 11 at the Moscone Center in San Francisco, based on Apple bookings discovered by Cult of Mac.

If Apple releases the iPhone 5 in October, it will likely just show a sneak preview of iOS 6 at the June conference. At last year's WWDC, Apple engineers showcased the Mac OS X (operating system for Macs) and gave a glimpse of iOS 5.

iOS 6 is expected to have major updates and flagship new features. However, Apple has not yet released any information about the new software to developers.