Do you not think may - just maybe - they have something special planned for the new imacs and want to save it for a special event? Like a keynote?
Maybe they will have retina, maybe it will be an all new design, maybe it will be more then that.
Just chill out, the current Imacs are no slouch, your just being a bunch of impatient, power hungry people who want the next best thing everyday.
Maybe Apple will just give it a minor spec bump like it did with the Pro line?
Having just purchased an iMac for a family member, after having nothing but good experiences with iPhones and iPads, I really don't see the fuss about the iMac. My 3 year old Core 2 Quad system trounces it on the face of using the iMac straight out of the box, and back then it cost £300 less than the iMac does now.
I think we need to face up to the fact that Apple are more about fashion than they are about technology. The iPhone is the phone to be seen to have. The iPad is the tablet to be seen to have. Macbooks are the laptops to be seen to have. Desktops? Why would Apple care about those? Everyone knows that posers will pay top whack to have something that's new and fashionable.