The 2013 iMac could be available as soon as spring 2013. The Intel processors that are most likely to power it will be shipped by Intel in the spring, if a leaked list of the new range of i5 and i7 'Haswell' processors is to be believed.
Intel's Haswell chips are the successor to the 'Ivy Bridge' architecture used in the current iMacs. Haswell will use the same 22-namometer process used in the current Ivy Bridge chips, but Intel has built a new architecture for it. Improvements offered by Haswell include faster performance and improved integrated graphics thanks to the new Intel HD 4600 graphics package.
According to the list there are 14 new desktop processors ranging from an entry level Core i5-4430S 2.7GHz quad-core (turbo boost to 3.2GHz) and maxing out at a 3.5GHz quad-core Core i7-4770K (turbo boost to 3.9GHz), according to the leaked document on Chinese site, VR-Zone.
As yet there is no news on the shipping date for the new range of Intel processors used in the Mac mini and MacBooks. The Mac Pro currently uses Xeon server chips, so it is unlikely that Apple would use a Haswell chip in that machine, which it promised to update in 2013.
Intel is also said to be working on a 14-nanometer architecture codename 'Broadwell'.
Recently rumours started to circulate that Apple was considering ditching Intel as processor supplier, taking its processor development in-house.