They can change the kWh simply by changing how they define empty and full without changing a thing in the battery pack itself. Also keep in mind that you can't just change the pack arbitrarily. There is a minimum delta that depends on the configuration of the pack.CS agent today told me the emphasis of the Large vs Max pack is in miles of range, not kWh, AND that the kWh may have changed from the 135/180. He didn't say it had changed, but MAY have changed. Hard to say if he really knew, but emphasis on miles per pack at this point.
Now an improvement in the batteries realized by the cell manufacturer since the 135/180 numbers were published is possible. But clearly no information on the actual battery capacities will be forthcoming.