According to the image of the Galaxy S4 successor, the device will be 133.3 millimeters long and supports a screen of 5.25 inches which corresponds to previous rumors . We also see a QHD Super AMOLED screen type, which would mean that the Galaxy S5 indeed features a display with a resolution of 2,560 x 1,440 AMOLED. The pixel density (ppi) might come down to 560ppi
Seriously though, is it worth it? I mean, it'll take tons of CPU and battery to run that many pixels that you can't even see. I mean, the entire point of "retina" displays is that you're not going to be able to see the pixels, but there is a point where adding more pixels just won't make any difference than on a spec sheet.
Even when TV manufacturers makes LED TV's slimmer and slimmer there is still an actual use case for those superslim sets, and 4K video on a 60" TV is still not retina resolution. Well, it is when you're sitting in your couch, but then again, so is 1080p.