The government of the United States is not about to take away your guns. While a disarmed citizenry may be in the interests of governments initiating unconstitutional acts against its citizens, taking guns from the hands and the homes of the citizens of the United States is not going to happen.
Eventually, as we develop more deadly ways of killing our enemies and each other, stricter regulations regarding possessing dangerous weapons will become law. Hand held phasers such as the ones used in the Star Trek series will replace the handgun as the weapon of choice. Will we allow citizens to own weapons that will vaporize people leaving no trace of them behind? You could vaporize someone in the cereal aisle of the supermarket and they'd never be seen again. There would be no evidence of foul play.
Physicists will tell you that the science required to manufacture a phaser is entirely possible. What I suspect will happen is that only the military will be allowed to possess a weapon with the power to vaporize. Citizens will have models that can be used to kill game or stun someone, but they won't be allowed military versions just as fully automatic weapons are prohibited now.
The Founding Fathers never imagined semi-automatic weapons with magazines holding fifteen rounds when they drafted the Second Amendment, but they did have the foresight to create an amendment that accommodates innovation.
Running around zapping people with ray guns will be as common in the future as drive by shootings are today. Until we evolve out of it, violence will be part of the human condition. Whether it's a musket or a phazer, man will always have access to a weapon to defend himself or to kill others. No matter what century it is.