I'm thinking coil guns instead. Room temperature superconductors don't solve the rail erosion issue with railguns, but I think should greatly increase the performance of coil guns.

My thinking is that zero resistance through the projectile itself and through the rails would help, but you still need to make an electrical connection between the projectile and the rails. Either this is done with a plasma arc or physical contact, but either of these causes erosion of the rails even if there is no electrical resistance through the rails or projectiles. Am I missing something?

Coil guns seem like they'd last longer, wonder what the performance figures for coil vs rail are.

For future rail guns, they'd just have replacement rails available as they do barrels for tanks/artillery guns (that wear out after about 1000 shots afaik).