Batteries are getting better and better. I guarantee batteries will see a doubling of energy density, there is WAY too much money behind it. I could see how the track becomes a way only to charge batteries and keep the lights on in passenger cars.
So now we get to add a consumable to our engines that guarantees the need for replacement in the future. Everyone says batteries are the future and the future for most of the batteries is the landfill, that is not very environmentally friendly. MTH dropped batteries when it went to PS3 electronics because people hated changing batteries when the super-cap does a better job for the life of the product with zero maintenance.
So we are still powering the track to run everything else, plus charge the battery so the battery can run the engine??? Here's a better way, dump the battery and run the engine off of track power, because it's already there for everything else.