The newest iteration of Jelly Bean allows devs to create app content in a variety of pixel densities to allow for the fact that there are a whole range of screen types that run the software.
The Extra Extra High DPI of 480PPI was previously the max, but digging through the code on eagle-eyed developer spotted 640PPI - that's Extra Extra Extra High DPI (or XXXHDPI if you're strapped for time).
That's Ultra HD territory.
Gives, takes away
Notes in the code add that "Applications should not generally worry about this density; relying on XHIGH graphics being scaled up to it should be sufficient for almost all cases."
So no Ultra HD new new Nexus 7 3 then? So what's the point?
The comments go on to namecheck 4K television screens, which suggests that Google has bigger plans for your TV than just its popular Chromecast peripheral.
Photosphere also gets some love in the Android 4.3 update; the panoramic photography tool should now stitch your photos' portions together more accurately as well as improving colour consistency.
Via Android Police