Historically, car companies have not offered upgrades to powertrains. However, the relative simplicity of electric car technology may allow that to change.
It has been a good two years since Tesla stopped manufacturing their Roadster, their first production model.
Elon Musk, CEO of Tesla Motors is now suggesting a production of replacement and upgrade battery pack option for their first production car, the Tesla Roadster. The Roadster, originally sold from 2008-2012, had a pretty impressive 245 mile range to start with. Not much information about pricing was released but Musk stated that the new replacements might have around a 400 mile range.
Similarly, Nissan offered a replacement battery pack for their electric car, the Leaf, for a relatively small price of $5,500, and it will also feature some of the newest battery cell technology.