Apple will be hosting an event on the 9th of March but 9to5Mac claims that the new music streaming service will instead be launched at WWDC. It is unclear as to why Apple might choose WWDC over their 9th of March event, so perhaps the service is not yet ready. The report goes on to state that there is a chance the service will be bundled with iOS 9 which means that its release will most likely be in the fall which is when Apple typically releases their next major iOS build.
It also turns out that the upcoming music streaming service will not be exclusive to iOS devices. Word has it that Apple is also developing an Android app that will allow Android users to subscribe to their new music service. Given that Beats Music supported the Windows Phone platform, we have to wonder if Apple will eventually extend support there as well as BlackBerry.