The Intel CPU in the MacBook Air was developed over the past year; it's state of the art and an enormous accomplishment.
The motherboard in this computer is not much larger than a typical soundcard!
There is also the machined aluminum case; if it's anything like the new iMac, this tiny notebook as as solid as a rock.
Will the next generation consumer Mac be nothing more than a keyboard with a Quad-core Mac, 4GB of RAM and SSD built-in, as well as an iPod Touch (or optional iPhone) that also functions as a wireless multitouch mouse?
In many respects, the framework for this speculation already exists.
Personally, I think the MacBook Air is essentially a flagship product from which future products will be developed.
The philosophy behind the development of the MBA is the key to it's relevance in the current mac lineup, not it's technical performance, per se.
There's more to computing than gigahertz and gigabytes; the device should fit into the lifestyle of the consumer, not the other way around.
I see it the same way. Technology that was developed for the Air will make it into new machines and influence all future Macs. Much like car manufacturers. Most people can't afford a Porsche but they sure do like the innovations that the German brand have filtered down over the years.