If you are wondering why the Air wasn't really revamped much this last time, it is because you are looking at plan B. Plan A was basically a low power Llano in an Air shell, and that would have been a really tasty machine. Instead of awful graphics with questionable drivers, you would get many times the GPU power but lose a bit of CPU power. I don't know anyone who wouldn't make that tradeoff. (Note: Anyone not employed by Intel that is .)
According to multiple SemiAccurate sources, one of the big reasons Apple decided to scrap the Llano Air was because AMD couldn't supply enough chips. They would have had to shift already thin supplies to Apple which would have angered their other customers and caused a lose-lose situation. So Apple went back to Intel.