No one really knows if the MBA will be redesigned in 2014. But it is very, VERY likely to happen. Why? Because of the following reasons:
(1) Apple redesigned the MBA in October 2010. almost 3 years ago. In 2014, the current design will celebrate its 4th anniversary. Apple (a) redesigned the original MBA (in October 2010) less than 3 years after its current release (in January 2008); (b) redesigned the unibody MBP, by releasing the rMBP (in June 2012), less than 4 years after its release (in October 2008); (c) redesigned the iMac (in November 2012) for the last time 3 years after its release (in October 2009). See a pattern here? Models are usually redesigned before 4 years. It's a guess, of course, but an educated guess. There's a big chance Apple releases a redesigned model in 2014.
(2) Competitors are getting better and better. Ultrabooks are becoming more and more attractive. Microsoft announced a Haswell Surface Pro, which is a tablet with laptop capabilities; Sony released the Vaio Pro, very thin and light, and seems to have gotten ultrabooks right now; Asus announced the new Zenbook with a 2560x1440 resolution; Acer upgraded the S7 series to get more battery life and a 2560x1440 screen; Samsung already released the Ativ Book 9 with a dazzling 3200x1800 resolution, taking the crown of the rMBP as the highest-resolution laptop in the planet; Lenovo announced new versions of the ThinkPad and the Yoga which are very thin and light, have stellar battery life and have very high resolutions; Dell announced the convertible XPS 11; and the list go on. Ultrabooks might have been crap in the past, but they are improving year after year, and the Haswell processor allows them to be real beasts. And now there is the Bay Trail platform, which will allow convertible tablets with good performance to be released for as low as US$ 500. Some of these new offerings are mouth-watering. Of course you may say that all these products run Windows, and that Windows is crap, and that OS X is far better, and all that Apple fanboy speech. But will that alone stop people from buying them. Can Apple get away with a 3-year old MBA design relying on its brand and on its operating system? How long can Apple keep its old design to compete with offerings that are getting better and better every year?
4 years is an eternity in tech's world. When Apple redesigned the MBA in 2010, it used a Core 2 Duo processor on it. We're already four generations ahead. Next year, we'll be five. Let's just be realistic. The world changes, and Apple, being the huge company it is, knows exactly what to do.
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Yes, but Apple doesn't work exactly this way. Once in about 3-4 years, Apple completely redesigns its product. Apple doesn't do these incremental upgrades much. It does revolutions. Look at the current MBA chassis. Basically the same version as the 2010 one. Same size, weight, thickness. Same materials. Same screen. The tech may have improved, but the carcass is still the same.
Apple kept the 2008 MBP chassis unchanged until 2012. Then, it revolutionized everything with the introduction of the 2012 rMBP, with its dazzling screen, thinner and lighter body, all-flash memory, and so on.
Apple updates its products year after year. But the big breakthroughs come with the redesigns.