On the other hand modern batteries for mirrorless have twice or more the shooting time of batteries for DSLRs when they dominated the market (manufacturers paid special attention to this to improve video times).
I'd say for photography, it's beyond what most would care about anyway, you can go shoot 300-400 pictures all day and not have to recharge. And if you need to shoot longer, you could carry a pound or less battery in your pocket.
The weight will be offset by the much smaller weights of mirrorless cameras and mirrorless camera lenses - as the former don't need to carry a prism mechanism, and the latter can be made smaller and closer to the sensor area.