Apple is now also rumored to update the iMac along with the Mac mini, MacBook Pro and the reveal of the iPad mini.
Apple is rumored to start selling an new iMac starting October 24 according to AppleInsider and MacRumors. Next week looks like to host a major Apple product launch. Besides the new iPad mini, we expect now Apple to release new Mac mini computers, a new 13-inch MacBook Pro with retina display and new iMacs.
The new iMacs are likely just getting new CPUs and maybe some new storage option. I do not think we will see a display upgrade to retina grades.
Apple is expected to host a media event on October 23 to announce the iPad mini and all the other new product updates.