No, I think you guys are missing the point. What does maintaining the same performance, or u-series processors have to do with anything?
The MacBook Air's intended buyer doesn't prioritize power and performance. If they did, they wouldn't even be considering the MBA! Maybe they simply want the same ultra-thin laptop experience, with a display which matches the level of quality they are used to from their iPhone and iPad. The MBA is for the buyer who values portability! Without compromising on core functionality. (I.e., still needs a keyboard and Mac OS, with the option of connecting peripherals, but not needing to connect dual Thunderbolt-peripherals at the same time, in which case they'd be looking at the rMBP).
The intended buyer DOES NOT CARE if it uses a logic board size of bare minimum, if it uses a Core m/i5/i7 of 5 or 15 or 28 watts. Only people at MacRumors do. The intended buyer will walk into an Apple-store and see a fancy new laptop, in three new colors, with a super-slim breathtaking design. They will pick it up and think "my old MBA feels like such a brick. I gotta have this!". They won't be browsing forums investigating whether it's got a 28/15/5w processor, as long as its fast enough for them!
Can we all more or less agree on this?
Now, if you're still saying that Apple couldn't provide a better 13" option than the 13" rMBP for those people, I say you're completely wrong. The 12" MacBook shows the future of a portable option. There is no reason why it couldn't be offered in different sizes. I'm sure Apple could make a 13-14" model, catering to the old 13" MBA users, which would make the 13" MBA and 13" rMBP feel like bricks!
Now, if it uses a Core-m processor, then so be it. As I said, I believe the fanless processors is the new segment which will improve greatly over the next couple of years! In 2-3 years they'll probably offer 90 % of the same performance as the equivalent 15 w model.