I expect there will be scaled modes like there are with the Retina MacBook Pro's. So you'll be able to use a desktop that's effectively 2560x1440 pixels like th

I expect there will be scaled modes like there are with the Retina MacBook Pro's. So you'll be able to use a desktop that's effectively 2560x1440 pixels like the 27" Cinema display. It's going to be pretty heavy on GPU's mind. The rMBP's do it by rendering a 2x density frame and scaling it down for the display. This means the GPU will have to render a 5120x2880 pixel frame and scale it down to 3840 x 2160.