As someone who doesn't follow superconductors, what sorts of things about life/engineering/society would change, how dramatic would it be, and more importantly: which stocks would you pick :)
You’ll still get better magnets and sensors, probably. Maybe even get new types of circuitry.
Just for comparison—we use silicon for integrated circuits. Not because it has the best performance, but because it’s convenient, it’s readily available, silicon dioxide is a good insulator, etc.
It's an interesting idea worth exploring. The two places where I think feasibility may face challenge is in the energy density gated by critical current density and magnetic field and in raw discharge rate (giant inductors are not known for being able to change their current quickly).
Knowing peak capacity and aging is also tricky since you can't measure critical limits without hitting a quench (a very, very bad scenario). You'll need to maintain healthy margins so you don't have things blowing up on sunny days or after so many charge/discharge cycles.
https://en.wikipedia.org/wiki/Superconducting_magnetic_energ...
Compare with this table:
https://en.wikipedia.org/wiki/Energy_density#In_chemical_rea...
Maglevs are also a popular guess - safer, faster, and more power efficient ground mass transport would be a huge thing.
Maybe even magnetic rail space launches.
And, of course, military applications (the last few examples I mentioned involve acceleration of big-ish masses to surreally high velocities, which is popular approach to weaponry).
So in addition to any immediate practical applications there's also this element of cracking a famous long unsolved problem. It'd be like if we discovered definitive proof that P != NP, or a theoretical basis for FTL communications. Even with no immediate practical applications it'd still be huge news.
I wouldn't say that it was necessarily "theoretically possible," for there has never been, and there still isn't, a grand theory of how any given material's atomic/crystalline structure relates to superconductivity. In other words, with no theory of material superconductivity, it was never quite clear what's possible and what isn't. With this new material, though, we might get a lot closer to a working model, if nothing else.
Which would enable us to put a lot of solar power in the desert and move it around effectively to other places on Earth.
Again, with the right material properties it could also produce efficient storage, and that also has huge implications for electrical generation.
If you lose 20% to the grid, then build a 20% bigger solar farm.
Solar farms actually help with reversing desertification by reducing water losses from direct exposure to sunlight.
Compared to the discovery of fire, the changes from room temperature superconductors would be a flash fire.
People would have suggested things like cities in the sky, looking down on things, and traversing marshland easily.
The actual main use for planes has turned out to be fast long distance travel. But we don't actually theoretically need to be up in the air to travel fast or far - in fact, had we never invented the aeroplane, we'd probably have cars or trains by now that moved as fast as present day planes do.
The revolutionary effect of new inventions is often hard to see, particularly for basic science research like superconductors.