Soon is a bit misleading. Those breakthroughs take many years to reach the market, if they ever, and even then they take a while to be reasonably priced. If it ever pans out at all...
But yea, it will come eventually.
By then mp3 would probably no longer be the standard anymore. And dedicated players would probably no longer exist. (it will be a cellphone+video+mp3+browser+etc).
Anyways its not a "500TB MP3 player in research". It is a 0.32 nm transistor technology (or maybe that is a misunderstanding by the author of the article, happens often) that COULD be used to EVENTUALLY make SSD drives 500TB in size. Considering you can already have a 128GB SSD drive and place it in an MP3 player... it is only to be expected that "eventually" we will get to 500TB. This might be the budding of the technology used to actually achieve this.