This won't happen for many reasons. First of all, we are too civilized. Second, the dog is not guilty of anything - it just obeys commands. Third, a police dog is treated as a police officer when it is necessary to classify you as a threat. And fourth, what LEO will allow you to draw a firearm in his presence? The LEO can draw and fire under 2 seconds because his holster is not obstructed. How fast could a common citizen draw from a concealed carry holster under a jacket?
The transition from the all-polite society to the shoot-on-sight society will have a huge hysteresis. Many people will let themselves be killed just because they cannot make themselves believe what is about to happen. As I said, we are too civilized. A caveman would have no problem here. But we are not cavemen; at first we will refuse to see evil even when the evil is in front of us.
I was thinking more along the lines of a sniper who’s a member of a street gang. A police dog is a serious threat to this bunch, and they’ll take it out.
I agree, though, that nobody is about to shoot a cop’s dog while they can be seen doing the deed. It’s suicide. Dorner level suicide-by-cop. And the cops will get a *lot* of leeway from the citizens as they start cutting though them. But if the State doesn’t take out millions of people overnight, I think you’ll start seeing Regulators coming back. But they won’t be targeting lone ranchers minding their own business this time.