Mobile phones are on the brink of breaking another pixel density record as the Sharp has declared its first 4K smartphone screen. The 5.5 inch panel will have the resolution of 3860 x 2160 pixels for the crazy density of 806 pixels per inch.
The IGZO display uses a standard RGB matrix, which means there are not going to be any problems with sub-pixel rendering. Not that those were quite probably given the density of the panel.
Sadly, mass production of the panel is proving to be crafty and Sharp does not anticipate to be able to reach it before sometime in 2016. If you’re really keen to try the newest super sharp technology, you’ll need to wait for at least another year.
And in the event you are thinking about whether a 4K display will actually make any change, you should look at GSMArena’s post on pixel density. There is an easy test there that allows you to understand the maximum resolution that makes difference for you, depending on your own eyesight.