I bet there won't be any Retina in the MBA line for the next 2 yrs. Apple is not ready to converge the line, they still want to drive buyers to the higher profit margin MBP line with Retina. And, the model for MBA is thin, light, portable, not a "pro workhorse" type machine, even though many people report it does work for them in that capacity.
I believe it will take them 2 yrs (at least) to figure this out and decide what to do.
I believe it will take them 2 yrs (at least) to figure this out and decide what to do.