I think the problem is more about making the system man portable.
Of course...but this isn't for a 120mm main gun, either, but when you consider what would go into this, and how much miniaturization has taken place in the past 20-30 years, I'm surprised this hasn't appeared earlier. We've had scopes with laser range finders for some time. I'd think the biggest challenge to miniaturizing an Abrams fire control system to a rifle sized weapon would be the thermal imaging system...of course you would have a sniper, and not a gyroscopically stabilized turret so there's still some human factor involved.
Now what they need to do is make a smoothbore .50 with a fin stabilized, discarding sabot .30 dart with a muzzle velocity in excess of 5K fps. That would be the shiz.