Ok, while the 2012 model will be shipping before year's end I am thinking that perhaps I should wait for the 2013 model.
I am considering this as the Intel chips (Ivy Bridge) for 2012 was released mid-year and the next Intel chips (Haswell) for 2013 is scheduled for release as early as March.
I am concerned that if I get this year's model Apple will make it obsolete in less than 6 months instead of around 12.
Just speaking out my worry. Really trivial.
Apple will offer both the 2012 iMac and 2013 iMac with Retina display? Built-in GPU would have double the performance by then so it could drive the lower-end model.
Apple typically (a) updates the iMacs with the latest Intel tech AFTER they update the MacBook Pro with them, (b) updates the iMacs every 8-10 months like the MacBook Pro, and (c) sticks to that schedule. Of course, they didn't this time and they didn't in 2006 when they unveiled the first Intel iMacs just three months after the iSight model iMac G5s had come out. Similarly, Apple did just introduce the 4th generation iPad much sooner than they had the 3rd after the 2nd, and the 2nd after the first, respectively, but those exceptions are much more rare. My guess is that you will have a good 8 months, at least, before Apple discontinues these new iMacs. It is highly unlikely that Apple will release Haswell iMacs when Haswell comes out. They didn't release Ivy Bridge iMacs when Ivy Bridge came out. Similarly, they didn't release Sandy Bridge iMacs at the same time that Sandy Bridge came out.