Apple's Worldwide Developers Conference is taking place from June 10 to 14 in San Francisco. The annual event is meant to showcase any new software or hardware, offer feedback to developers and encourage them to keep the App Store buzzing with new third-party programs.
Last month Tim Cook confirmed that we'd be seeing the new version of iOS, unofficially dubbed "iOS 7,". Apple might give an idea about that in WWDC: 2013. Judging by pricing leaked to 9to5Mac, it appears at least a new version of the MacBook Air will be unveiled at WWDC.
Apple is in fact rolling out its own online streaming music service. Recent developments such as Apple locking up deals with record companies like Warner Music Group and selling audio ads, indicate a push to have the service completed in time for WWDC.