Don't expect the MBA with retina until the Intel Broadwell processor is made available to OEMs. This is the only way the MBA can have retina and yet still have respectable battery life, though if you compare MBA retina broadwell with MBP retina broadwell, it's hard to imagine how Apple can design the former to have more battery life.
I think due to the delay of broadwell, Apple decided to refresh MBA this year instead of announcing MBA retina. I agree with the other comments that Apple will rather keep MBA with a long battery life than go back to the early days of MBA where the battery life is short and the ultraportable MBA is not that portable since you have to bring the charger everywhere you go.
If you can wait, then wait. If not, you need to decide between the portability of MBA vs the MBP's retina screen.