This is a concept, so the production version will be a bit different, but overall the shape will be pretty much what we see here. They will of course lose the glass side panels and roof, both to be replaced with carbon fiber panels as is the entire outer shell. If you compare it to the renderings in the post below this, you see it is kind of a hybrid of a few of them. There haven't been much details released yet, but some of them of note that I did read are the car will have tall 19" wheels, which are very large diameter for a car of this size. The stated purpose for these are that they lower the rolling resistance and improve efficiency. It will also go 0-60 in under 8 seconds. It will charge on a regular household 110v outlet in six hours. That basically means the battery pack is small as previously reported, probably 16 to 18 kWh. It will also have a range extender option that BMW calls i-REx. The range extender will be a small gasoline(not diesel) engine that will only charge the battery pack, it will not have the ability to drive the wheels directly like the Chevy Volt can under certain circumstances.
I'm sure there will be lot's of info coming out in the next few days, I'll try to get it all up here as soon as it's available.