There's lots of things to do with extra electricity, it's just a question of whether or not it's economical. Here in California, for example, I could imagine the excess being used to opportunistically desalinate water and refill reservoirs. If water and emissions were priced appropriately, it might be worthwhile? It's not exactly a battery, but it's a way to make overbuilding more palatable.

Alternatively if the grid is unreliable, end-use customers will install their own batteries and generating capacity. Voila, problem solved on someone else's dime!