Well 0.6 J/GH at the chip isn't <0.5 J/GH at the wall. I honestly could give two craps about the at chip efficiency unless the company selling them is willing to a) pay for all the non-chip power use or b) I was designing my own miner and buying raw chips by the reel.
The 'at the wall' power includes not only the chips' power consumption... but also the Controller's power (which isn't going to change much between now and next 6 months)... and includes power supply & dc/dc converter inefficiencies... which isn't going to change at all and hasn't changed for years... so even if the chips consume HALF the power of their previous generation... the rest of the system is still going to be a drag to halving the 'at the wall' power.