Folks wanting an iMac with Retina display will be happy to hear that some evidence has surfaced in favor of the mythical machine. The recently-released OS X Yosemite developer preview includes a new file that defines display scaling resolution options for an iMac.
The native resolution of the computer is not mentioned, but the file includes a series of scaling resolution options that max out at 6400 x 3600 pixels, or 3200 x 1800 as a Retina display. It’s likely the display will scale down to a lower resolution like the MacBook Pro…
The first of these resolutions indicates hexa “00001900 00000e10” is therefore a resolution scaling of … 6400 x 3600 (probably 3200×1800 HiDPI).
Continues and is 5760×3240 (2880×1620 HiDPI) 4096×2304 (2048×1152 HiDPI), etc..
(There are other resolutions, just make the conversion from hex)
With this alone, it is not possible to guess the native resolution of the machine. This is a resolution that does not appear in the file, since it is native and does not have to be “scaled”.
Knowing that there is a gap between the values of 5760 and 4096, one can imagine something between these two (probably 5120×2880, 2560×1440 or in HiDPI), but this is speculation.
A Retina iMac has been rumored to be in the works ever since Apple introduced its MacBook Pro with Retina display in 2012. But it’s likely it ran into issues of component capabilities, pricing, or both that that kept it from mass-producing the higher resolution panels.
The last time Apple updated the iMac was in the fall of last year, which included processor speed and storage bumps. The computer was completely redesigned in late 2012.