New MacBook Airs are coming. Here is why

The MacBook Air (s aapl) looks destined for a refresh very soon, and the latest sign is that Best Buy (s bby) began listing existing models as “Not Available for Shipping” over the weekend (via 9t05Mac). The retailer is thought to be shifting its remaining stock to stores to make room in the distribution center for the arrival of new, updated MacBook Air models. Amazon (s amzn) is also showing low stock of MacBook Air models in many of its international stores.

Stock shortages and third-party retail inventory systems have traditionally been a fairly accurate barometer of Apple’s hardware refreshes, especially when an update is close at hand. Best Buy’s website revealed new MacBook Pro SKUs ahead of their official release, for example, in February, when the notebooks got updated with Intel’s (s intc) new Sandy Bridge processors.

A MacBook Air refresh has been rumored for a while now, and part of the update is thought to be the inclusion of Sandy Bridge processor architecture. Intel recently unveiled new low-voltage Sandy Bridge chips, including a Core i5 1.7 GHz variety and two Core i7 versions, one at 1.7 GHz and the other at 1.8 GHz. Current MacBook Airs still use much older Intel Core 2 Duo processors, so the new Core series are a near-certainty for powering any new hardware.

Another change likely in store for the MacBook Air includes the addition of Thunderbolt, Apple and Intel’s new high-speed I/O port. Apple has been steadily replacing the Mini DisplayPort on its new Macs with Thunderbolt. This is because Thunderbolt can handle display output as well as data transfer functions and is compatible with Mini DisplayPort cables and adapters. Other possible additions include a FaceTime HD camera, something else that both the updated MacBook Pro and iMac got this year, and a switch to an AMD (s amd) graphics processor, since Apple seems to be methodically cutting NVIDIA (s nvda) out of that part of its business.

An updated MacBook Air likely won’t arrive at this point before OS X Lion, which Apple has said will make its debut in July. People who purchase new Macs as of June 6 are eligible for a free upgrade to Lion, so Apple can save itself some money by just shipping new MacBook Airs with the new OS installed, instead of having to deal with the administrative costs of providing a refund. Both Lion and new Airs could ship as early as next week.