According to MacLife, 10-15th June is the most probable date for WWDC conference this year. This is deduced from the calendar of activities of Moscone Center, the convention centre where the event takes place for ten years.
The Moscone Center’s schedule already lists four events for June – the traditional month of WWDC – leaving the week of June 10-15 as the only five-day stretch starting with a Monday not already booked.
The Apple World Wide Developer Conference has been held in early June for the past six years. Apple usually Announces WWDC in late March or early April. Last year Apple waited until April 25th, to reveal the exact dates & sale of tickets, the event was sold out within two hours thereafter.
The expectation is that Apple will unveil iOS 7, iPhone 5S, Cheaper Version of iPhone and most possibly next generation Mac OS X. Recent reports claim that upcoming handset and software are already being tested on Apple’s campus, and pictures claiming to show the internals of an iPhone 5S have appeared online (check here).