Thanks. What a shame though, most likely there will be some "hacks" to use the iMac with a pixel for pixel mode, like the "hacks" thats available for the rMBP but, 5120x2880 pixel for pixel on a 27" monitor i guess everything would be supertiny and unusable.
But this makes me wonder even more why Apple haven't just released a 4k Apple Cinema/Thunderbolt monitor because Mac Pro users, do they really want to run the future 5k monitor (if they will ever release one) in retina mode. Don't they just want more screen realestate? (sure, just buy a 4k monitor from another brand but i am curious what Apple's perspective is)