It never ends, does it?
What about the 2053 MBA?
It doesn't appear to end.
However, it seems to me that the 2014 MacBook Air will carry a major redesign, perhaps the most significant since the laptop was released back in 2008.
In 2010, the MacBook Air went through a major redesign, but the exterior of the 13-inch model did not carry much of a difference, although it is thinner, lighter and overall a bit smaller.
But the 2014 model will probably represent a milestone in MacBook Air's history so far. And, contrary to the 2053 model, it will be released in a few months from now.
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I doubt that apple is gonna achieve significantly more battery life with a thinner design and retina display... unless the Broadwell chips are super efficient.
The Broadwell chips are expected to have a 30% battery life increase over Haswell, despite both processors sharing the same architecture. At least that's what Intel is bragging about. We shall wait to see. Not too many people were believing when Intel said that Haswell would bring a boost in battery life, but look at the battery life of the 2013 MacBook Air and other Haswell models... it lives up to the promise (or at least, almost does). Broadwell should be even better.
In addition, Apple could put IGZO displays into the MacBook Air. Apple is reportedly looking at these displays. And Dell has just updated its XPS 15 with an IGZO display, so there's really some competition here. These displays are known for its battery-saving capabilities. IGZO displays were developed by Sharp, and are so fancied that they are expected to save Sharp from bankruptcy. IGZO displays are the reason why companies as Apple and Samsung are investing heavy in Sharp. An IGZO display is said to have triple battery life than an ordinary display. Even if these numbers are heavily exaggerated, you may have an idea of what's coming.
And, of course, OS X Mavericks is supposed to bring improvements in battery life... but let's see in a few days how that goes.
So, battery life should be great even with a very thin design.