Exactly. The potential market for grid storage for renewables will be similar in size to the market for EV batteries once the cost of battery-backed renewables falls below the cost of a grid connection. And once that does happen, power grids worldwide are going to rapidly enter a death spiral as their fixed costs are spread between fewer and fewer users.
Why? The role of the grid will still be arbitrage between power generation and power consumption. A flat in a high-rise in a city doesn't have anywhere to put solar panels; a factory couldn't possibly sustain its power consumption with on-site renewables, and no amount of on-site battery storage will change that. Somebody needs to buy power from net producers, and sell it to consumers.
Yes, of course power sinks gain value from having their own power buffer, even if only to take advantage of fluctuations in energy cost. But why would this cause grid collapse? They still need the energy delivered, at some point. It puts whoever runs the grid in the quite enviable position of power market middleman. Far from collapsing, I would expect grids to do extremely well out of such a shift.
