Interesting Point!
In my opinion, WEC is pioneering technology, which can be adapted to other forms of racing, so first they brought hybrid engines, which F1 implemented in 2014. There are rumours that the WEC may open its regulation to fuel cells.
So in my opinion F1 should be a hybrid formula in the longer term, maybe with spec parts to get or keep costs down, and when fuel cells are ‘ready’, f1 can implement them into their power-unit-formula. But I think this is a process which can last decades maybe?
I cannot see a sprint or endurance series which is based purely on batteries as an energy storage, unless research grants a small battery with a decent capacity which can be swapped quickly at a pit-stop for example.