10,404 sets with 37,711 difficulties take 57.7 GB approx., and there are no videos. What osu! shows in main menu is the number of difficulties, not beatmap sets.
Even if you download all ranked maps, that'd be only about 120 GB at most, given you want them with no video.
Nobody really knows when the body dies. After brain death, and then organ failure, and all the electricity's gone, a rotting corpse still feeds the world, mother's diesel for the biological engine of life. Who knows where the internet will go, or for how long, or in what strange aeons it will return? Who can say if ours was even the first?