I think the main problem with current energy storage methods is not energy density, but cost.
If FF golden age brings the cost of most materials and manufacturing down, we will not have storage problem anymore.
If you want to you can make liquid fuels from air co2 and run internal combustion engines off that, where the FF generators do not work.
Still for those who are betting on non-near-fusion future, storage technologies should look like a an attractive investment.
