“The official launch time for Apple Music is June 30 at 8 AM PT, per a Rogers’ blog post and Facebook event, at which time iOS 8.4 will be made available for users to update their devices.
iOS 8.4 is required for Apple Music, which shouldn’t have too much impact on adoption; Apple enjoys likely the steepest upgrade curve anywhere for OS upgrades, and it’s unlikely that 8.4 will run into any issues like the size constraints that prevented some from updating immediately to iOS 8 when that major new version launched. . .
. . .the traditional history of iOS updates is that the debut window for the software can encounter issues that delay availability of the software, due to things like a whole bunch of people all attempting to access the update from Apple’s servers at the same time.”
Thanks to TechCrunch