Earlier, the developer behind Instapaper, Marco Arment published his thoughts on the potential timeline for upgrades to Appleís iMac and Mac Pro lines. In it, he suggested the need for an ultra-high resolution 5120x2880 Retina Display (either inside the 27-inch iMac or as a standalone display) is likely the most significant hurdle preventing major updates for the specific product lines.
Anticipation for new Retina iMacs has been high since the previous rumors which stated Apple was planning to bring Retina Displays to its next-generation iMac line and suggestions of updated models were rumored to be right around the corner. Unfortunately for Apple and iMac fans alike, Arment is now hearing that although the next iMac update will come later this year, it isnít likely to include Retina Displays. He mentioned the following in his post:
Iíve now heard from multiple sources that while an iMac update is indeed coming this fall, it will not have Retina displays.
One possible reason is that the Cupertino California company is waiting to release OS X Mountain Lion in late July with the intent of following last yearís trend of launching the new line of iMacs, Mac Pros, and even Mac Minis alongside Mountain Lion. The speculation however remains unconfirmed and there isnít any evidence to provide concrete information regarding the matter.
Source: Marco Arment