What displays are capable of displaying full resolution from the new MacBook Pro with retina display?
There are all sorts of high end specialized displays that have this resolution for the medical, government imagery, and engineering markets.

http://en.wikipedia.org/wiki/Graphic_display_resolutions

You can see any Hyper XGA display exceeds 2880 by 1800 (but are not shipping as single monitors yet) and most Quad XGA displays (shipping since 2001) exceed the "15 inch retina" in terms of sheer pixels on one display panel/monitor.