Technology is bringing us closer and closer to Star Trek type weapons. I know that the military was working for a long time with Laser weaponry as well as rail guns and the next generation of weapons to fight wars with. It's my understanding that the great limitation with a lot of these weapons is the power required and once that is solved then we will see these weapons implemented on many different platforms. I think it's very likely that given the power requirements of many of these weapons that miniaturization of nuclear based power sources may be where they are headed. As for the way to achieve this nuclear based power safely, such that it could be incorporated in say a single airplane or drone unit may be the current, largest, obstacle to overcome. Either way the next World War could be an unrealistic science fiction type conflict where machine guns will be looked at in pretty much the same way muskets would be looked at compared to the 50 cal machine gun.
A battlefield where truck based laser platforms or tank based laser platforms would have the capability to literally cut down or cut apart troops in massive unbelievable numbers and close in combat could be seen with Star War type light sabers.