There is more potential for energy savings than water savings with dishwashers. Because dishwashers already use a relatively small amount of water, there is little financial incentive for consumers to spend more money for products that use less water. This is not the case for energy.
Dishwashers use energy primarily for heating water and secondarily for circulating the water through the machine. To the extent that the amount of water used by the machine can be reduced, the energy consumption can also be reduced. New high efficiency dishwashers have more effective washing action, energy efficient motors and other advanced technology such as sensors that determine the length of the wash cycle and the temperature of the water necessary to clean the dishes.
In the coming years expect to see the energy and water efficiency of dishwashers improve, but baring some dramatic new technological development it seems unlikely that these efficient products will take as prominent a role in the market as efficient clothes washers.