When will Macbook Air + Retina Display, come out?

My 2011 Macbook Air has taken a hit from the latest update to Mountain Lion, and I have my eyes firmly set on the Macbook Pro with Retina Display. But I cannot justify the expense and must resist the consumerist urge. But the additional kg or so, kills the deal for me.

I love the weight of the Macbook Air; the ease of holding with one hand, as with the Macbook Pro, with the quality build, makes it a nomad's dream.

Anybody care to share when they expect the Retina technology to trickle down the Macbook Air range?