Nissan is teasing the aerodynamic improvements of the new Leaf.
The roofline does look much better than the current Leaf, and the underside shown in the profile, also has a slight rise, which looks consistent with what it should be, for lower a Cd. It would also be consistent with neutral lift.
I think they have kept the quieter air flow around the side mirrors – the arched chines on the hood seem like they are doing that job.
The wheels and the wheel openings look tighter and close to flush, which will also help lower the Cd, as well. And the trailing edges are crisp (rather than curved away from the air flow, like the current Leaf) is critical for lower drag.