Makes absolute sense to me, and this is actually what I would like to believe will eventually happen.
Now if you want to argue specs between the two, number by number, then it's pointless to debate about it.
Average consumers are not tech savvy, nor do they spend their hours on forums such as MR, quibbling over rumors and random speculation of core iX processor this, or SSD that.
Given that benchmarks on the Air models have proven to be suprsingly close to that of the 13" MBP (thanks in part due to the flash drive), the average consumer won't have a care in the world that his/her machine is using an age old processor thats 1000 Mhz less than it was before, as long as the machine functions perfectly and adequately.
I also have first hand experience on the whole ordeal. I own a new 11.6" Air, which replaced a 13" MBP with 8GB RAM before it, and performance flies, thanks again to the flash drive. I honestly don't feel any performance hit at all. Not enough at least to care about it. It does what I need it to do and for average consumers, that's going to be the only thing they need to care about.
Why convolute the lineup with machines at the same price point? This is the only two Mac products that conflict with each other in terms of pricing, so one of these has to go. Apple may just combine the two, axe the "Air" suffix, but retain the specs of the Air in a new era in the Macbook line. But who knows?