Understood, my mistake. This is pure speculation, but I doubt you'd see those in consumer electronics. Those energy storage devices would essentially be very power electromagnets and I really don't think people would be walking around with those in their pockets. I do agree that they would be super useful for grid-level energy storage though! If you can engineer around the large magnetic field they'd create it would be a super efficient energy storage device!

Also, sorry in advance - this is me being nit-picky, but that would be more analogous to replacing a battery with an inductor (not a capacitor). Inductors store energy in magnetic fields, capacitors store them in electric fields. Doesn't really matter... I'm just being pedantic.