This may be more of a "Mac perhiperhals" topic, but seeing as no other Apple computer could power this right now...
http://anandtech.com/show/8496/dell-previews-27inch-5k-ultrasharp-monitor-5120x2880
Requires 2x DP 1.2 streams, PPI roughly equal to that of the rMBP. :drool:

http://anandtech.com/show/8496/dell-previews-27inch-5k-ultrasharp-monitor-5120x2880
Requires 2x DP 1.2 streams, PPI roughly equal to that of the rMBP. :drool: