Energy storage is going to be huge, but probably low-margin. Anyone who can buy batteries can be in that business, as with solar. The biggest grid-scale battery operation in the US, Manatee in Florida, uses battery modules from Samsung. Not Tesla.
Selling equipment to utilities is profitable, but not hugely so.
Energy storage also strikes me as a scenario where it is trivial to shop for the best deal. There is no halo around a product for industrial users who are just looking for technical specs given price. Worst for battery manufacturers, I assume it is straightforward to mix and match brands/technologies as the grids expand over time.
Selling equipment to utilities is profitable, but not hugely so.