No, they can and I am sure they will do some of BOTH i.e. reduce the number of cells for about 10% and still make a pack with a bit higher capacity, power and lower weight. It will have better acceleration, lower average power (less prone to overheating) and better range at lower price than full option 1.That should be exciting. Given the Model S uses 3100mah vs the 2400mah cells in the Roadster, they can either:
1) Keep the same number of cells and get 1.29x the capacity (72kWh) and power (only useful if they upgrade the firmware/motor/power electronics to use it).
2) Keep the same capacity and use less cells, shaving 22.6% the cell weight (~150lbs) and volume (plus whatever overhead).