We previously heard a rumor about a new 21.5 inch Retina iMac with a 4K display, the device was originally spotted in the OS X El Capitan beta.
Now according to a recent report from Mark Gurman, Apple will launch their new 21.5 inch Retina iMac in October.
The new Retina iMac will apparently be announced along with the release date of El Capitan in October and will then go on sale at the start of November.
The new iMac will feature a 21.5 inch display with a resolution of 4096 x 2304 pixels, it will also come with new processors and the device is said to retail for more than the current 21.5 inch models.
Apple is expected to offer two version of the 21.5 inch iMac, one with the standard display like the current model, the other with the Retina display.
Source 9 to 5 Mac