I've blogged on this before, predicting the digital download would all but disappear in as little as 2-3 years ... and here we go.
The market-dominating iTunes will cease to offer downloads to 'own' (the legal status is controversial, but ownership is clearly restricted compared to physical media) from 2019, as streaming surfs to the top of Apple's, and the wider music industry's, strategy.
The dominant mode of distribution not so long ago is rapidly disappearing, though I'm sure some smaller sites will continue to offer DL options. How many major artists will bother offering this? Could still be quite a few - many digipak and vinyl sets come with DL codes for MP3 or even FLAC files.