Power efficiency is not a major consideration currently. It's still price per GH.
Depends on when those chips are installed into miners and go into production. At the current rate of difficulty increases, a miner going into production today produces twice as many BTC as one going into production in 52 days on October 7. For this reason, a lot of expect that rate to slow down - but it has not slowed down yet.
![](https://ip.bitcointalk.org/?u=http%3A%2F%2Fi59.tinypic.com%2F2vmzupx.jpg&t=663&c=FTIF9b1Yrcs3Fg)