Tesla just announced :
Also being announced today is that the small battery option for the Model S will not enter production, due to lack of demand. Only four percent of customers chose the 40 kWh battery pack, which is not enough to justify production of that version. Customers are voting with their wallet that they want a car that gives them the freedom to travel long distances when needed.
The customers who ordered this option will instead receive the 60 kWh pack, but range will be software limited to 40 kWh. It will still have the improved acceleration and top speed of the bigger pack, so will be a better product than originally ordered, and can be upgraded to the range of the 60 kWh upon request by the original or a future owner.