The original MBA was a dog performance what relative to the previous Mac lpatops. It is in part because Apple moved before the technology was fully mature. It was enabled enough to make a product but not a fully mainstream product.
This is likely another generational shift that is built far more so around what is coming over the next 3 years out of Intel's pipeline than component products that come out 3 years ago. The MBA 4-6 years ago was priming the pump for the MBA 2013-2014 models. So thing is likely happening here.
The whole thing about "Air" was about dumping ports. The connectivity was suppose to shift to "over the Air" that's why Air is in the name. Wifi is faster more widely useful now ( e.g., Display over Wifi
http://en.wikipedia.org/wiki/WiDi ). Bluetooth is faster and more widely useful now (e.g., point-to-point ad hoc high sped networks is what makes Continuity work) . Those factors are going to get weaved into the models that are pushing the 'Air' concept.
It think you have it backwards to an extent. The last couple of years the MBA, especially the 11" model, actually took up the position of the MacBook/PowerBook. Entry level (affordable) laptop that comes with a couple of compromises but can get basic jobs done (maybe with alittle help from externals). That is really the what want. Not what the Air was originally.
This "as slim as possible" is actually going to back to the Air roots that the MBA has been drifting from. It probably won't be the "most affordable" Mac laptop anymore. It would help if Apple just retagged the products.
MBA 13" --( logical broadwell update ) ----> Macbook
MBA 11" --- ( via upscale to Retina and even slimmer diet) --> 'next tech evolution ' Air model. MBA 12"
Over time the "horsepower" will come back as the SoC (CPU+GPU+Chipset) technology incrementally moves forward. Same thing happened last time as Flash and "lower voltage" tech incrementally moved forward.
The display is only incrementally more and the Core M is incrementally less. The chipset and radios are less. There are no 100W ports to power. [ I wouldn't be surprised if port can't do higher than base USB 3.0 spec power charging if the high charge ports move off to the power brick. ]
Most computer users don't wander to client sites and can only connect with Ethernet. The issue is that these "I need to use 3-4 ports at the same time" users are a relatively shrinking set of the market. It isn't that they don't exist, it is just that they don't dominate the market. All the more so in the markets that Apple sells into. Apple isn't trying to sell to the same fixed, limited subset of customers forever. That's never been the company's core mission.
Most mainstream workloads probably can run off of internal battery only for a whole day's worth of work ( 7-8 work day). iPhone can be charged with handy external battery pack that is far more portable than any laptop (even if don't get phone charging power brick with new model ). Huge swaths of folks just use Wifi. Another huge chunk use wireless headsets. Collaborate data sharing over web services ... more than a few use every day.
Free the port from power , display (why paying extra to Retina if not using it most of the time?), and TCP/IP traffic the one port left over can hold a dongle for a legacy USB device.
Apple's jihad against wires had drawn more than a few "wire haters" to them. Neatness, simpler seekers ( if don't consider the RF spectrum). This whole nuke ports thing is hardly new either. Apple pushed Thunderbolt adoption by going wholesale into port adoption. Likewise with move to Lightning. Suspect same thing will happen with USB Type C over slightly longer product rollout schedule ( 2 years rather than just one. )