We don’t need the price of solar or batteries to keep falling, or for large exponential growth to occur. Simply maintaining the current rate of solar energy installs over the next 25 years would result in a renewable heavy grid.
China is currently on pace to install ~300 GW of solar power in 2024 assuming they continue that for 25 years and give a minimal 15% capacity factor that’s already at 100% of their current electricity consumption before those panels hit end of life. Granted, demand would increase over that time period but keeping up with demand doesn’t require crazy exponential growth here.
Grid batteries are in a similar situation, companies aren’t installing them at scale because they don’t need to but there’s plenty of excess battery manufacturing capacity right now to fill the need as it shows up. Basically at current rate of renewable installs there becomes an economic incentive to slowly ramp up grid batteries.