Mobile phones are on the verge of breaking yet another pixel density record as Sharp just announced its first 4K mobile display. The 5.5" panel has a 4K resolution of 3860 x 2160 pixels for the insane density of 806ppi (the Highest in the world, so far).
The IGZO screen utilizes a conventional RGB matrix, meaning there aren't going to be any issues with sub-pixel rendering. Not that those were very likely given the density of the panel.
Unfortunately mass production of the panel is proving to be tricky and Sharp doesn't expect to be able to achieve it before sometime in 2016. So if you are very eager to try out the new super sharp tech you will have to wait for at least another year.