They become irrelevant as soon as massive energy storage becomes cheap. But as it stands now, fusion seems more realistic than cheap energy storage. But who knows what people come up with.
Cheap energy storage is far more realistic than fusion. I'm amazed you could think otherwise. Simply extrapolating cost reductions of Li-ion cells down their experience curve gives cheap storage, and there are hundreds of alternative chemistries and technologies that could also work, and that can be demonstrated more cheaply than any fusion reactor.
