Time to dig out this old thread!
Looks like the time has finally come, according to 9to5mac.com, the new iMac 21.5 will be release next week with a resolution of 4096 x 2304.
Source: http://9to5mac.com/2015/10/06/apple-planning-to-launch-new-4k-21-5-inch-imacs-next-week/
PS: No, the fonts won't...