Most likely an accurate prediction and I totally agree with that. However, you forget that that is only the medium. You still have to buy the music to put on it.
If CD-quality/hi-res downloads come down in price, then cool, fill them up. If they don't come down, we're still going to have to get the physical media first to get the music cheap for those of us that don't want to spend more than around $10 an album. And just remember, you can't buy "used" downloads (well, really you can but it's not really legal at the moment and not feasible legally without DRM, which is a sucky system on anything

).
And for cloud-based stuff, there's all sorts of issues with that. Low bitrates (in a lot of cases right now), slow speeds, network dropouts, excessive data charges, phone battery life, rights battles with the record and streaming companies (i.e. they probably never will have everything), doesn't work when the power/network is out, etc. Then there's the EMP (it could happen). Could it work perfectly? Yes, but only in a perfect world. We won't be there for a long time. My biggest issue is when you're driving through an area with spotty cell reception or when you're out of the country and your cell phone doesn't work. Even the perfect infrastructure elsewhere will not help you stream your music in those cases at the moment. Sure, you can use Wi-Fi, but you also have to be relatively still for that to work. Also, there's the possibility that the NSA is watching you or something. What if one of them decides I listen to too much metal? (I joke but it's not impossible for that to happen.)