Before you count Mac Airs out of competition, try Windows 8 - it is unfinished.
Well, I have tried Windows 8. Have you or are you just reading what people post on the web?
Windows 8 is a weird beast. It is not an unfinished product. I wouldn't say that. I have the Release Preview installed on my computer. It boots very quickly, quicker than any other OS X or Windows that I have tried before. It never crashed with me. Nothing unfinished about it.
But the "metro" or "Windows 8" interface, or whatever Microsoft chooses to call it, is very weird for someone using a conventional laptop. However, it is not difficult to get used to it. Window management is better under Windows 8 - and if you look deeper, it has similar advantages to using Mission Control in OS X.
In addition, Windows 8 has multi-touch capabilities, in both the screen and the trackpads, that we haven't been able to test yet in our laptops - and they will add functionality to the OS.
It is a bold move for Microsoft, and it won't please anybody. In fact, the press is thrashing it before launch, and it certainly won't be a success like Windows 7.
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We definitely won't see a refresh, let alone redesign, until Haswell.
Honestly, there's not too much they can do. But I really think they can make the 13in chassis smaller.. or alternatively, shove the 13in panel in the 11in chassis and a 14in panel in the 13in chassis.
There will be a redesign, sooner or later. The next spec bump will be when Haswell is released, probably. But what about a redesign? It may come with the next refresh, or it may come even later. But, considering that the MacBook Air was last redesigned in 2010, it is not too far away.
A redesigned MacBook Air would perhaps be a little bit lighter, use different materials, and accomodate internals in a different manner to accomodate a retina display and a larger battery.