While not a tangible benefit for them, they do get a more secure network as a result.
I don't think you can neglect the price of a new ASIC in a real situation though, those things are very expensive. Where it was first possible to attack the network using regular hardware, it now requires a much bigger capital investment. When ASICs were first released they had a bigger advantage than they have now, it seems unlikely a 2x improvement over the previous generation is still possible (assuming it was possible before, I didn't check).
Right, I'm not saying there will be a new ASIC; just that there will be no innovation in the Bitcoin space (unless they switch out of PoW) that leads to less energy being used.