in pistol competition the use of electric switch activated from the non aiming hand is forbidden
it is used to avoid the trigger pull unbalance , as a safety requirement , the rules state that the trigger must not activate at less than one kilogram force
the shooter aim and press the switch with its free hand
yes the firing time is can only give a small improvement the loading extracting remain
there were some attempt at combustible shells , solving half of the problem but creating new one
increasing the rate of fire just result in more ammo consumption ,
there also is the ever present problem of overheating
of course the final evolution of personal weapons is throwing rocks
Even lasers are theoretically guns as they are throwing charged particles out a type of barrel... I mean if you want to say anything that projects force and is carried by hand is a gun variant then it is quite difficult to say what would replace that. Nothing until humans are mostly removed from frontline fighting in warfare which seems unlikely to happen for quite awhile for quite a few reasons.
Once the robots take over maybe it will simply be enough to show a demonstration of capabilities and the weaker side runs algorithms showing in so many years they will be overwhelmed and simply surrenders and adapts to the winner's demends (basically Borg).
While humans are involved gun varients will rule until there are eye based attack systems with cybernetic interfaces that allow aiming by looking and thinking so the actual weapon could be in a satellite overhead. Maybe if some type of shielding is invented against physical projectiles it will be back to Dune with slow fighting blunt or not very sharp weapons that don't trigger the shield to react (since air, moisture, sounds would need to pass the shielding in some form).
I do think drones will be the main evolution in the near future especially as VR headsets and near field communications improve. Soldiers in an urban battlefield will still carry sidearms but the main 'fighting' will be between drones hunting enemy soldiers/vulnerabilities with small teams of drone operators infiltrating warzones to bypass jamming systems that make sitting in a trailer in Nevada and flying a drone over Yemen impractical. (unless quantum entanglement becomes militarily deployable then wars will be whichever side can build the most efficient drones the quickest while protecting their civilian infrastructure from cyber and biological attacks).
The world is increasingly becoming more electronic. In a few centuries, we will likely become integrated with our machines as well. In that context, cyber attacks will likely predominate. There may be counters to cyber attacks but cyber attacks have a few advantages over physical warfare. They are instantaneous, cheap, and perhaps most importantly you can directly attack either the intellect of one component of the enemy system or the entire system as a whole. Understanding the political context of a war can frequently determine whether or not it can be won. With cyber attacks one can attack the enemy will to fight directly. Physical altercations are a messy way to solve problems when power can be taken more efficiently by influencing the political will of your opponents. You don’t need to physical beat anything down if you can just convince them to go along with what you want.
In the short term, gunpowder based projectiles may be phased out as our ability to generate and store energy increases. Things like railguns are already on the horizon, the only issue is that our ability to generate and store energy is not advanced enough to make weapons like this handheld.
Also, there is potential for us to revolutionize our non-lethal weaponry. We are currently stuck with things like rubber bullets, tasers, and pepper spray, but these all have many issues. Police action in the future will rely on AI surveillance systems that catches criminal behavior instantly (this already exists now in some places) and eventually drones may take over the role of police officer.