http://www.appleinsider.com/articles/12/07/04/supply_of_apples_27_imac_drying_up_as_ivy_bridge_upgrade_awaits.html
Looks like a July update will come with the Mountain Lion Update.
The early report https://www.macrumors.com/2012/07/03/more-claims-of-october-launch-for-updated-imac-models/ of an October update looks a bit unlikely given that iPhone 5 will arrive at around that time. One possible reason for an October update would be lack of NVidia 68xM (680M?) GPUs. Time will tell.
Looks like a July update will come with the Mountain Lion Update.
The early report https://www.macrumors.com/2012/07/03/more-claims-of-october-launch-for-updated-imac-models/ of an October update looks a bit unlikely given that iPhone 5 will arrive at around that time. One possible reason for an October update would be lack of NVidia 68xM (680M?) GPUs. Time will tell.