Neither of those things are correct - this is based on a ground-up new EV chassis, called MEB:
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(click on image for link)
And it is not some "body" they are already building. It is not unlike the Nissan IDS Concept:
http://youtu.be/iErN6gh3veU
Volkswagen I.D. EV Concept Photos and Info – News – Car and Driver
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