It's been a while since Apple made any major changes to its hardware, but a new MacBook Air may arrive as soon as next month.

While last week the tech world mostly buzzed about Google and its annual I/O conference, the rumor mill has now turned back to Apple and its rumored refresh of the popular MacBook Air.

According to Apple Insider, stock for the popular 13.3-inch MacBook Air virtually vanished at large online retailers such as MacConnection. That model packs a 1.8GHz processor and a 256GB solid-state drive. Best Buy still has the laptop in stock, but it's the "only reseller on AppleInsider's Mac Price Guide that is currently advertising available inventory," reports the Apple-centric publication.

While this is by no means a confirmation that Apple is preparing to launch a next-generation MacBook Air, vanishing inventory at authorized Apple outlets is typically a strong indication that a product refresh is imminent. When a next-generation product is about to enter the market, previous-generation models are generally going out of stock to make room for the shiny new toys.

If a new MacBook Air is indeed imminent, one question lingers: what will Apple pack on the new laptop? At this point it's quite safe to assume that the next-generation MacBook Air will sport Intel's next-gen Haswell chip, as well as improved graphics. Intel's new processor will make its debut in early June, and Apple's annual Worldwide Developer Conference (WWDC) will follow shortly, which of course prompts speculation that the Cupertino giant may introduce a new MacBook Air with Haswell on board at WWDC.

What remains unclear at this point, however, is whether the new MacBook Air will sport Apple's much-touted Retina display. Slapping a Retina on the next-generation MacBook Air would make a lot of sense, but those displays involve a lot of additional costs and can negatively affect battery life in thin designs. That doesn't mean it's out of the question, but it's difficult to tell for now.

The thinnest MacBook boasting a Retina display is the 0.75-inch-thick MacBook Pro. Compared to MacBook Air standards that MacBook Pro is quite thick, partly to accommodate a larger battery. On the other hand, high-resolution display technology is advancing at a rapid pace, so Apple could find a solution and cove all fronts.