I think the point that is counter to yours is that we are nowhere near the fundamental limits of energy density for batteries. It's probable we are near a fundamental limit for LiPo, but the point is that battery tech improves by changing technologies/chemistries. BEVs couldn't exist at all when the best rechargeable battery tech was lead-acid, but were enabled by LiPo. Theres most likely a type of battery you can't even imagine that has yet to be invented that could store >10x or more energy than current LiPo per unit cost or mass.