Universities aren't stupid; they know there's no threat from dropping JSTOR and they can count to $50,000 all too well.
And every university already has a unified accessible non-JSTOR system for reading old journal articles: its called the journal stacks in the library basement + interlibrary loan. Everyone already knows how to deal with that: its just less convenient.
> I know that every university, there are multiple servers where students share terabytes of pirated movies, TV shows and music.
You are being delusional if you think such a system is at all comparable to what it would take to replace JSTOR for all but a fraction of university JSTOR users.
I was a technically inclined CS guy with far to much free time while in university and I would be royally pissed if my university had dropped JSTOR for some sort of ghetto fileshare with an aging torrent. Anyone a less ideal user than I would be crippled by that.
Academics are quite used to being creative in acquiring articles. It's not untypical to ask colleagues and friends at other universities to scan and email articles that they can't get access to through their own library. Before the advent of the Internet this was done with letters. Downloading a torrent is a minor inconvenience in comparison.
A large majority of people I have talked to have at some point acquired scans of at least on book online (be it to give it to students because the library has only one copy, for convenience during travelling or because the local library has no copies and an interlibrary loan would take some time while they need the book now).
Not to say that pirate servers aren't hanging out on Uni nets these days, but they are stealthed, and deniable.
Nor would anyone hesitate to prosecute one of us (yes, I am a grad student) if we were to share an archive on BitTorrent.
"Universities aren't stupid"
Really? Part of my introduction to grad school was an annoying quiz about complying with copyrights and a bunch of reminders about the penalties I would face if I dared to infringe. Yes, really, my school takes copyrights that seriously, and guess what? My alma mater also subjected me to that sort of treatment during my undergrad orientation.
Do you really think universities are prepared to stand up to the copyright system? Do you think any mainstream university is going to suggest that people download an illegal archive of scholarly publications? I can tell you this: I would be shocked if any respected university official endorsed the use of an illegal archive of scholarly articles, textbooks, or anything containing even the tiniest amount of human knowledge.
There is no way in hell any university in a developed nation would drop their subscription to JSTOR. JSTOR keeps them on the right side of copyright law, keeps itself up to date, and provides infrastructure that the vast majority of university users find essential.
Individuals not affiliated with universities may find such a pirated collection useful, but such individuals currently make up a fraction of one percent of JSTOR's revenue.