An iMac with a retina display would likely be much more expensive than the current line. And I'm not sure a 27" iMac with retina display would be very practical considering the resolution would be very high making everything on screen so much smaller. Also, the normal time between iMac refreshes has varied from 12 to 18 months. There was also a time when the refresh occurred in less than 12 months. In other words, we have no idea. So, enjoy your new iMac and stop worrying about what's ahead.