What about the mac mini? Surely if the iMac has been delayed because of a redesign of the screen and/or form factor no such excuses for mac mini.
Given mini's status as the entry level offering for people who don't care about specs and (generally) already have a keyboard and monitor they want to use, it may not be updated this cycle. It wouldn't be the first time the mini went on a 2-year cycle.
The Mac Pro went on a longer cycle for different reasons.. Sandy Bridge-E being way late among them.