Wouldn't interest me in the least, it is just going to use more power and raise the price. Aside from that, the pixels are already small enough on the MBA. Putting even more of them on the same sized screen would do nothing for me.
Actually, when Apple labels a screen Retina, they are only referring to the size of the pixels related to viewing distance.The Air needs a better screen regardless. The TN panel is a joke now. I'm sure when a Retina screen comes to the Air next year, the price/battery won't change. Also keep in mind that a Retina screen is not about making the pixels smaller.