While on the surface it sounds like a low level "win" the most likely outcome is every part that makes up a firearm will now be serialized and require a 4473 to purchase.
That'll take legislation. The issue the ATF faced is that an AR Lower (complete) doesn't actually meet the definition of "Firearm" in law, and the judge said that they can't just say "well it's the closest part to the definition in law, so that's the gun." Which, of course, is exactly what they did when presented with an AR for the first time.
The biggest, obvious thing here for someone with time and money to fight is the whole "third hole is instantly a machine gun" thing*, but I doubt there's rich enough people willing to fall on that sword.
When this first came up a decade or so ago, they kicked it back to congress to change the law, but nothing happened. I expect the same thing will happen here, and life will proceed.
ETA: *and bumpstocks. There's very little chance that bit of rulemaking will survive a judge.