no way. they considered it for iOS 9, but losing just those few months between this month and fall (aka September) is time that they can't really afford to lose. Also i think they probably feel like it's time...it's been over a year since the Beats acquisition, it would only hurt them by delaying.I always said that since iOS 8.4 dropped as a beta that it would be completely possible it would never hit the update block. I honestly think 8.4 was just a test of the new interface to not only see how people liked it but if it was stable enough. It will show up in iOS 9, but I don't think they will bring this whole new interface to iOS 8 especially if all devices that can run iOS 8 will run iOS 9.
On a bigger point, there is going to be enough bugs and instability that naturally come with a full number release that they are going to need to fix...not even taking into account that this year is going to be focused on overall stability. So add getting a new Music app design + streaming service off the ground to the pile of work for iOS 9 just doesn't make any sense when they can avoid it.