If you think the iMac is out of date, check out what Dell, HP, etc. are producing. Sure they have high-end Ivy Bridge models but they are still shifting plenty of models that are completely out of date by Apple's standards, using much older hardware than the 2011 iMac's.
Can I buy an Ivy-bridge desktop from HP or Dell? Yes.
Can I buy one from Apple? No.
The processors came out in April, almost 6 months ago.