Agreed, but I think more likely never. We already have trains competing on time against aircraft on many routes and they'll get even faster. That is far more economic. It may be that the only time in future we take to the air is for crossing wide oceans, but advanced sophisticated communication could even rule out most of that with holographic meetings.That means in volume terms to hold equal energy battery would need to be 7 times size of fuel tank...Thats before we look at weight/ mass.
Perhaps in 200 years.
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