[FireWire]

Now that 4K displays are available for under 800$, it's tempting to get one. However, I wondered if 4K displays will be treated like a retina display (HiDPI) and scaled like the rMBP, or it will simply display ridiculously small icons/text?

[P]

Short question, but somewhat complicated answer. Anand tested all of this in his Mac Pro review:

AnandTech | The Mac Pro Review (Late 2013)

The TL;DR is that it's hacky to get something useable. First you need to have a solution to get the picture from your Mac to the display, which either very low update frequency (30 Hz) or a hack on top of DisplayPort 1.2. Apple supports the hack from their side, but the display must to, which apparently requires you to pick from their list of tested displays. If you can get past that, you get 2560*1440, which is the same as the 27" iMac. You can get it to either native 4K (really tiny text) or HiDPI of 1920*1080 using SwitchResX, but you apparently cannot set it to a HiDPI 2560*1440 and scale down the way you can on a rMBP.

So basically, you need a Mac with DisplayPort 1.2 (which is confirmed to be the rMBPs and the new MP, but could be others as well), Mavericks, and SwitchResX, and the best you'll get is HiDPI 1920*1080.

[FireWire]

It's a shame that 4K is better supported on Boot camp (60 Hz, high resolution) than on OS X on the same machine... So, without hacking, they are expecting people to use really small text? Even my 2560x1440 27" is quite small... So long for the resolution independence they announced 10 years ago...

[FireWire]

Too bad the current 4K displays are "hacks" as I was considering ditching my Dell 2713HM for a new 4K, for a little premium. My current dell is already a hack, requiring a display override to use the RGB color space and for it not to be seen as a TV by OS X, not supporting the native resolution via HDMI and having trouble with sleep... As it's new I could get it exchanged. But I'd like to use the 4K display in Retina mode. I'm always amazed by the quality of my built-in display when I'm not using my external display!

[P]

This is the sort of thing a point update can take care of, though. Not scaling down from even
larger than 4K, because that may be the largest your GPU supports, but the need for SwitchResX and a special list of approved displays can be fixed in a 10.9.2.

[ghporter]

There is a lot more demand for bleeding edge display technology in the Windows gaming world than there is in the entire Mac world, thus more attention given to driving 4K displays with Windows. My take is that, given some additional time and more, more affordable 4K displays (and TVs) on the market, and the video card manufacturers will drive inclusion of Macs in the mix, without hacks.

I typically have had coworkers ask me "how can you read that tiny text" when seeing me use my 2006-vintage MBP with its 1440x900 native resolution and default text size. I think a display that is essentially 4 times as fine-grained, with probably 1/4 the default text height would require microscope specs to read!

On the other hand, for video, that sort of resolution would allow you to actually see things that are only hinted at with lower resolution displays, sort of the way going from a good DVD version of a movie to a BluRay version lets you see things like "Oh, you can see individual people on the walkway in this scene." On a recent visit to a BestBuy, I saw two different 4K TV demos running, one from Samsung, the other from Sony. Both were mindblowingly clear and crisp, with wide cityscapes in the Sony demo showing individual people on the sidewalk, from a vantage point that with standard definition TV you would only see smudges for cars on the street. These 55"-class TVs weren't even that much more expensive than my 55" Samsung LED TV (LED lit, that is) from 5 years ago.

I seem to recall back in the dim times when RGB was giving way to VGA, that progress came in fits and starts, with a variety of "not quite standard" formats hitting the street, only to be one-upped by some other vendor's trick. Overclocked video cards, tricking display timing systems, and all the other silliness that went with it all just made things harder for users. The advent of HD, "ultra HD" and now 4K has been much smoother, hopefully because everybody learned something from those bad old days.