Apple's big-screen 27-inch desktop Mac awaits Ivy Bridge upgrade

With the last iMac update having arrived more than a year ago, third-party resellers are now starting to see limited availability of Apple's big-screen 27-inch desktop Mac.

As of Wednesday, AppleInsider noticed stock-outs of the 3.7-gigahertz 27-inch iMac at Best Buy and J&R, while only a handful of units remain available at Amazon, where it is advertised that more are on the way (Update: Amazon's listing no longer indicates limited stock). In addition, MacMall is currently sold out of the 27-inch iMac with a 2.7 gigahertz processor.

The lack of availability at Best Buy is particularly noteworthy as the retailer's website simply states the all-in-one computer is "not available" both online and in store, with no indication of a restock. In contrast, Apple's newly released MacBook Pro with Retina display is advertised as "backordered," with new orders expected to ship between 7 and 30 days from Best Buy.

Limited availability at Mac resellers is often one of the first signs that Apple is drawing down inventory ahead of a product update. And the iMac line is due for an update, with the most recent refresh released over a year ago, in early May of 2011.

However, it should also be noted that Apple's iMac desktops are a popular choice for education institutions. Last month, Apple kicked off its annual back to school promotion, offering a $100 iTunes gift card with the purchase of a new Mac, which could explain limited availability of the 27-inch iMac.

ust this week, a new report out of the Far East claimed that Apple's supply chain is currently gearing up to begin production of the next-generation iMac. However, that report suggested the updated all-in-one desktop won't become available until October.

The new iMacs are expected to feature Intel's latest-generation Ivy Bridge processors. Apple's MacBook Pro and MacBook Air lineups were upgraded to Ivy Bridge with a product refresh last month.

It remains unclear whether the next-generation iMacs will feature Retina displays like Apple's new MacBook Pro. Reports from earlier this year suggested the new iMacs would in fact have new high-resolution displays, though more recently doubt has been cast that the addition will make the cut for Apple's 2012 models.

Other rumors from this year claimed that the 2012 iMac refresh will feature new anti-reflective glass displays. That would be a first for the iMac, as Apple has until now only offered anti-reflective solutions as build-to-order options on its MacBook family of notebooks.