I'd say at most we might see some minor updates but it all depends if the retina iMac is part of the main line or a new model, aka the MBP.
Again if this is basically just an internal Ivy Bridge update then why couldn't it have happened back in June?
That's a bit of a understatement - "Should have happened in June".
You are absolutely correct, judging by the limited detail we have, the October 2012 revision of the iMac will be a slight upgraded design and upgraded internal components, i.e., Ivy Bridge processors - first available in April/May 2012, or six months ago, upgraded GPU's - hopefully top-end mobile AMD's, again available in June this year, USB3 and enhanced RAM/SSD options - nothing ground breaking whatsoever - indeed, the 2011 iMac still on sale today is already showing its age - although, Ivy Bridge processors only offer a 8-15% improvement in speed over Sandy Bridge in real life situations - hence biggest changes possible should have been GPU, USB3 and maybe move to top end wireless specs to future proof the machine a little - not being a great fan of SSD, I'd have preferred an actual hybrid solution in a 2.5in form factor as offered by Seagate.
Anyway, I'll only be looking at low end 21.5in iMac on this revision and will migrate to Haswell on my iMac 27in and Mac Mini when its launched eventually by Apple - hopefully June 2013 if Apple uses the road map it used with the updated October 2009 model, revised to i3/i5/i7 in mid-2010.
In a nutshell, Apple have lost US$2,500 sale from me this year - why invest in Ivy Bridge when Haswell is around the corner - my iMac BTO i7 27in is more than enough for now - although better GPU would be welcome as would USB3.