For the future, don't look to sci-fi movies (Hollywood doesn't think), look to science fiction novels and games.
Some advances I think we might see:
In the ammunition field -- caseless ammo eventually (hasn't provided enough advantage to make it worthwhile changing everything, that's why we don't have it yet). We may also see guns that use a liquid propellent, sprayed into the chamber in an aerosol similar to a the fuel injector in your car. This would allow adjustments to vary the velocity of the round, from subsonic for surpressed shots, to high velocity shots. And we might see some advances in bullets to improve their terminal performance, like practical explosive bullets, or a hollow point bullet that also includes a dense armor-piercing core, enabling one round to perform well against both armored and unarmored targets.
We'll likely see improved sighting systems for guns. Better laser sights, improved reflex sights and optics. All of these are becoming more common; ten years ago most soldiers did not have anything other than iron sights, now various optics and accessories are almost standard.
Railguns and other electromagnetic weapons exist, in laboratory form anyway. We won't see practical, man-portable versions for a while. I think the main problem is storing enough energy, then being able to release enough of that energy all at once, rather than in a trickle. Chemical propellent still provides that more efficiently than anything else we've got. However, when this problem is solved, electromagnetic weapons will provide the ability to accelerate a projectile to very high speeds.
Directed energy weapons like lasers, particle beams, etc. Same problem as for railguns, the power source. We already have lasers in the field, but mainly as part of sighting and ranging systems. There's a forward observer vehicle for artillery that mounts a laser capable of blinding enemy troops. A true laser weapon is going to require a lot of energy released all at once, and there are also environmental conditions that can make lasers ineffective -- rain, fog, smoke, etc. I'm not that knowledgeable about particle beams and plasma weapons, but here's a link for anyone interested:
http://en.wikipedia.org/wiki/Energy_weapons
Oh, and as far as lightsabers....we certainly don't have them yet. George Lucas writes space opera, not hard science fiction. To my knowledge, there isn't even a scientific principle that would allow it to function -- how to you create an intense laser beam that stops after 3 feet? And the problems mentioned above about the power source are even worse for a lightsaber, where you are constantly
wasting power.