Until the point when military lasers become high-power and small enough for the average soldier, I think we're still going to be using a firecracker with a metal pointy thing at one end for some time.
Now the components of said cartridge may change. You've probably heard of caseless ammo; instead of using a brass shell, the primary and shell are partially encased in a moldable explosive charge. It loads like a bullet and fires like a bullet, but once the bullet leaves there's nothing to extract and eject. They're being considered for aerial and crewed weapons; imagine loading a tank shall and not having to get rid of the old casing. An F-16 wouldn't have to carry it's brass back to base (no, they don't dump; collateral damage), saving fuel. Only problem with all this is that the "casing" is more delicate than a brass shell so the guns and loaders have to be very gentle with the shells right up until pin strikes primer. And of course, you invent a whole new way of making a casing which has not significantly changed in over a century, and it's going to have some steel initial production costs.
There are also rail guns; they have improved the technology to the point where a magnetic slingshot the size of a destroyer gun can throw a shell as far or farther than a gunpowder weapon, and here's the bonus; no gunpowder to squib or cook off. All you need is a hardened steel slug. That will definitely make ship deaths like that of the Hood truly a thing of the past.
Lastly, yes, they are developing lasers and microwaves as tactical weapons. A laser trained on a drone F-16 brought it down in about five seconds, and they're working on upping the wattage. A special microwave emitter can be mounted on a Humvee and used for crowd control to drive back approaching forces, and it isn't harmful for several seconds, while a jolt of less than a second gets you going in a hurry.
All of this can conceivably be miniaturized into something a soldier could carry similar to a SAW or M60. It will however take time; current caseless rifle systems are already there, but the round is too powerful for the average soldier to control, and too expensive for GIs to spend millions of rounds a week.
