I think a mixture of solar, nuclear, and other renewables is probably the best option. Electricity doesn't transport well over long distances, and what's best for one place isn't necessarily good for another. The economics of solar and energy storage vary around the world, depending on factors like clouds, and geography which can support pumped hydro (both lower and upper reservoirs). Solar might make more sense for California, and nuclear for St. Petersberg. I'm sure some combination of decentralised and distributed energy generation will prevail into the future.