i only listen to cassettes.
my assumption would be that nothing is going to happen to the media that you have downloaded or to the software on your computer and the media that you have on it. you would probably just have to upload it to the cloud. but the cloud is no guarantee either.
it does raise an important question that i have been interested in since i did my college work in history, working with ancient manuscripts that have been taken care of for centuries/millennia and books that have been in libraries for decades/centuries.
for the last 20 years there has been a push to digitize all media and get rid of musty old hard copies of books and microfiche and music that take up so much physical space. however, my contention is that it would be easier to lose mass amounts of digital data than it would have been to lose that data stored physically. it would likely take some kind of disaster on a large, if not global, scale. but that is more foreseeable than losing every academic and public library in the western hemisphere at once.
given the lack of human care, physical media can last for decades to millennia. without human care, digital media has a much shorter lifespan, even given the most optimal conditions. in the long term outlook, digital information is far more transient than is physical information.
i don't think it's a matter of if a library-of-alexrandria-type event will happen to digital information. i think it's a matter of when.