My daughter has a 4S on 7.1.1 that she uses as an iPod touch. She is getting an iPod touch 6 (since it has a larger screen, better processor and higher capacity) so I am getting the 4S back. I want to update the iOS version on it since I'd like to use Apple Music on it. Would it be better to update it to 8.4.1 now or wait for iOS 9?