Executive Summary: more complicated than you might expect.
Unlike previous attempts at higher low voltage systems, Tesla seems to have done enough at 48 volts to make it worth doing. In this Munro Live video you can get an idea how serious Tesla is to have done it right.
You may not know this but there was a previous attempt to go to a 42 volt system. That effort failed for an assortment of reasons from available technology to the lack of commodity availability of the higher voltage pieces such as window motors.
