Replacing batteries isn't wonderful for the environment, but they can be recycled and such.
Replacing a whole motorcycle is even less wonderful...batteries need to be recycled, metal needs to be (hopefully) melted down and recycled, various parts are hopefully reused...but usually most parts just end up in landfills. Even if the whole bike is recycled, well that took time and energy to do.
(it takes energy and causes pollution and a using of resources to build any vehicle...a car, a motorcycle a bike etc etc...the best thing always to to use that vehicle to it's maximum lifespan and then recycle it. Replacing your car every year or two is bad for the environment. Replacing a perfectly good Enertia after a year is also not great for the environment. Though selling it to a friend and the friend riding it for a full lifespan would help).
The bigger question is: while Brammo is not updating the batteries on the older enertias, well can either newer enertias or enertia plus models be updated...and can a customer like BrammoCommuter update his old enertia himself? Basically would need new batteries and a new battery management unit right??
Hopefully, while Brammo might not be committing to updating the old bike, there must be DYI options for some smart people to attempt.