dewalt announcement today.

Yes, and at some point the PCness filtered down from Mt. Olympus.

It was all I could do well. ;-)

it is all clear now

are they going up in voltage to increase power output and because the batteries are lighter or just for more power

All the arguments about battery pack voltages aside, higher voltage can be used to produce more torque. Motors have windings which all have some amount of resistance. This resistance results in a voltage drop and with a higher available voltage, the percentage of 'wasted' power due to the voltage drop is less. Motor torque is proportional to current. A higher voltage also lets you increase the available motor current and/or allows for more windings in the motor.

One early example of this 'voltage war' is people who upgrade old VW bug

-BR

lighter batteries now means they can keep the weight in control but still provide more power

my old dewalt was on the heavy side