Delay could be an issue with the fancy welding process being used
Apple CEO Tim cook has already told people interested in the new version of the iMac that there would be "a significant shortage" of the new computers. The cause of the shortage is attributed to manufacturing difficulties. A new rumor circulating that claims the manufacturing difficulties may push availability for the new iMac back into 2013.
The rumor originates with a "commercial source" he says that the new iMac computer may not be ready for the holiday shopping season. The source also speculates that the delay has been new with the welding process used to build the machine cases. The new iMac uses something called friction-stir welding that uses high heat and pressure to intermix the molecules of two aluminum surfaces to create a seamless joint.
The manufacturing process also has other complicated steps including a screen lamination process that eliminates the 2 mm air gap between the display and the front glass. Apple site still shows November availability for the 21.5-inch iMac with the 27-inch iMac showing December.