I've seen video of the 12 gauge "cordless taser" round. I'm sure it will remain scarce, expensive and effectively "Big Brother Only" for some time yet. Even the police style "wired" taser requires a lot of money and a lot of paperwork for Joe Ordinary to have -- and practice is not going to be cheap. Ordinary mortals will have to settle for handheld "contact stunners" for now.
Soft body armor has improved a bit. And it's being built into decent clothing. I know that's not Sci-Fi shield technology, but it may be worth acquiring.
Until power supply/battery technology makes another leap, and maybe a few other things happen - like affordable room temperature superconductors, I don't see laser personal sidearms becoming common. I love the idea. How can one not love a weapon with speed-of-light velocity, negligible recoil and totally flat trajectory?
There have been some advances in projectile design - and some "vanished" as quickly (anyone recall the French "Arcane" ammo?) as they appeared. Many years ago, I had a friend who experimented with compressed wax paper bullets. He felt he could make a cartridge/projectile that would be lethal at 25 feet, but harmless at 125 feet. He wanted to make a PDW about the size of a pack of cigarettes, effective up close but no risk to more distant bystanders.
Every so often, we hear about caseless ammunition. (Seems to me the original 19th century Volcanic was an effort in that direction.) I'm not holding my breath until it's affordable and common. And many of us handload. Handloading caseless ammo might be a bit too high-tech for DIY.
I can see room for improvement in muzzle brake design. I'd like a nearly recoilless pistol. But with the ridiculous sound suppressor laws in the U.S. I'd expect any such gun to be horribly loud.
I supposed the trend toward tiny, light pistols in substantial calibers can be taken a little bit further, but we're about at the limit of human tolerance now. Sure, I want something the size of a Baby Browning .25 that hits like a .44 magnum, but I also want to be able to control it.
We still haven't seen a tiny cartridge that hits like a big one. The only way I can see to do that is VELOCITY. Materials and propellants limit what we can do. And the shooter still has to be able to control it. And it should not deafen him.
The new Kel Tec PMR-30 (improved Grendel) is a step in that direction, and it's an attempt to carry enough rounds that there's not much need to reload or carry spare magazines. But the .22 WMR in a 4.3" pistol barrel isn't all that super a stopper. I did consider one of these for a MIL who isn't a shooter -- give 'em a couple of years to achieve reliability, then buy MIL a "house gun" that she can simply pick up and go bang - 30 times.
I agree completely with the comments that our overregulation totalitarian society has stifled individual creativity. I hate to say it, but the next great advances in personal weapons technology are not likely to come from North America.
And as my Beloved Wife reminds me, knives don't run out of ammo, are very effective at contact distance, and they have a psychological effect. As she puts it, "You can see it in your opponent's eyes. A gun says, 'I'm going to kill you.' A knife says, 'it's going to hurt a lot while I kill you.'"
So I'll go on daydreaming about the "Noisy Cricket" from MIB, but in the immediate future I still see chemically powered cartridge pistols and fine steel knives as useful, regardless of how "low tech" they seem to some.