Annual and long-tail storage are both problems that need solving, and fuel cells do look like a possible solution. But it's not clear at all what the winner will be for those applications.

Even hydrogen is competitive here. IMO, more competitive than that battery chemistry on the article.

Fuel cells are a possible solution (especially if one can build a dual mode electrolyzer/fuel cell), but combined cycle power plants burning hydrogen would also work, if only at very large scale (but then economical hydrogen storage likely requires large scale).

Seasonal energy storage is the last thing that needs to be addressed in the storage hierarchy. There are very high-value targets starting on very low time frames.

Seasonal energy storage is the last thing, but that also means it's the last caveat, as far as I can tell. If we figure out seasonal energy storage, that's it. Solar just wins. There's no further need for fossil fuels. We're done.

I guess there's still aircraft.