I am also about to pull the trigger on a 2013 13-inch MacBook Air. The only thing that is keeping me from going ahead and purchasing is the GPU improvements of Broadwell. I think that the current CPU and GPU performance in the 2013 Air is actually surprisingly good, pretty much on par with the Late-2013 13-inch Retina MacBook Pro (except the graphics perform better on the Air). I tested these two MacBook models in person at the Apple Store and the CPU difference between each other for exporting 100 high resolution photos to .PNG was just 8 seconds. Exporting and encoding video on the MacBook Pro was only slightly faster too than the Air. However, graphically, the Air outperformed the 13-inch MacBook Pro. Animations were super smooth, 4K video for 10 minutes never stuttered at fullscreen or when other tasks were running simultaneously, and I haven't tested this in person, but Skyrim via Boot Camp runs very smoothly.
I really hope that retina does NOT come to the MacBook Air. I honestly think that retina is overkill for computer displays. I sit approximately 2 ft. from my MacBook display when on a desk, and at that distance, I can hardly see the pixels anyway, they're even less apparent on the MacBook Air because of the higher pixel density. I might welcome a SLIGHTLY higher pixel count, but retina is ridiculous. It puts a strain even on the base model 15-inch MacBook Pro, which still has some choppy animations. I compared the Air vs Retina at approximately the same distance, and retina hardly makes a difference. It's only really seen if you sit closer than 2 feet, which I never do. 1440x900 on the 13-inch is pretty good, a bit more might be perfect, but retina is just a waste of GPU power.