There's another breakthrough I'm looking forward to, however - really good instantaneous pricing and metering. When prices are set on demand and fully automated, then energy caching hooked to the grid becomes viable. This creates a good arbitrage financial model. Store energy from solar/wind when the sun is shining and the wind is blowing, and sell that stored energy when demand is up and supply is down.
Once that's working, the whole grid gets remodeled. Then we can make a real dent in the coal-fired baseload plants and aging nuclear plants that desperately need retired. Economies of scale and experience will reduce production cost for whole suites of energy storage technologies (batteries, compression, thermal, flywheel, gravity, etc), even if they don't become more efficient.
That's an exciting future.
The combined cost of solar, batteries and grid changes, more advanced handling and software actually don't result in cheaper energy prices.
Compare California to places where they use gas.
It doesn't really need a revolutionary breakthrough, just for solar and battery costs to drop 50% or so such that they become the cheapest option. A 50% drop will probably happen just from the existing trends continuing.