As you can guess, these are both aimed for use in smartphones, or phablets, depending on your particular views. The two TFT LCD displays were manufactured using low temperature polycrystalline silicon (LTPS) technology, and offer a pixel density that is pretty much unrivaled, even by LG. The slightly smaller 5.4'' display achieves a pixel density of 543ppi (vs LG's 538ppi), while the 6.2'' giant has the very respectable 473ppi.
To put things into perspective, a 5-inch panel running a 1080p resolution, the current golden spot, has a pixel pitch of 441ppi, lower than even the much larger 6.2-incher, and considerably inferior to the new 5.4- and 5.5-inch screens from Japan Display. Of course, whether the human eye can discern such pixel-dense screens from a now lowly 1080p panel is a whole different story.
In case this hasn't been made clear enough, it does appear that the industry is preparing for the next jump in display tech, and we definitely expect to see quite a few smartphones powering similar panels in 2014. Seeing as Japan Display is a collaboration between Sony, Hitachi, Toshiba and the Innovation Network Corporation of Japan, it does appear likely that a 2014 Xperia may very well be one of the first such devices.