Mercedes-Benz, bless their hearts, are working on making their batteries serviceable, and on training people in rebuilding packs.
Apparently it can be done, with great care and moderately invasive procedures (you're working on something that has voltages of several hundred volts, and there's one step where you have to saw through the glue that holds the lid onto the "sealed" pack).
Their packs are designed to be modular, so you can replace bad modules (if not bad individual cells
), and they're thinking that servicing the packs would be something that would be done on a regional level -- sort of like the level of specialization you need for a transmission shop, or an automotive machine shop.
Hopefully it can be done -- right now dealing with the end-of-life issues of battery packs is the biggest Achilles heel of electric vehicles.