Opus is royalty-free, in contrast to mp3. And it will be used in WebRTC. I can see some devices picking up Opus to support WebRTC and possibly some (not portable music players, obviously) dropping mp3.

Obviously neither you nor I have a crystal ball, but I see Opus as the PNG of audio codecs - not displacing the lousy but entrenched de-facto standard (GIF/mp3), but slowly taking over at the technological edge.