Unfortunately, the 28” is going to have the wrong pixel density to use with OS X in Retina mode.
Non-Retina MacBooks start at 110 PPI. Cinema Displays have hovered around 100 PPI for about a decade, with the 27” Thunderbolt Display topping out at 109 PPI (same for its sister 27” iMac).
At 28", a 3840 x 2160 panel has a PPI of 157, which, dividing by two to get the equivalent non-Retina PPI, comes to only 78.5, a reduction of over 20% from the lowest-PPI Cinema Displays. This means, on a Mac in Retina mode, everything in the UI will be 20% bigger than normal. Maybe that’s something you could get used to, but it’s far from the much more optimal 24” panel, with a PPI of 184 (92 PPI non-Retina, very close to a 24” Cinema Display).
There used to be a flag for that. Starting in 2006, there was a special "DPI Slider" in Mac OS X that allowed you to set the resolution from 1.0 to 3.0. Each WWDC they claimed that by next year they'd activate it as a user feature, but that never happened. Instead we got retina mode. The reason probably is that they never really got all apps and all use cases to look terrific in all supported scale variants. I remember playing with it a lot from 2007 to 2010 and usually there were always apps (oftentimes even Apple apps, like Textedit) that simply looked awful at 1.3 scale or other variations.
Indeed. Acorn's RiscOS had resolution independence in the 80s with scalable fonts and icons being shipped as vector graphics; it's a pity everyone else is 30 years behind.
I'm afraid you're mistaken. RiscOS certainly had scalable vector fonts (anti-aliased too!), but the icons and interface elements were all bitmaps and the OS was not resolution independent.
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.
There was a time when DPI and PPI were effectively the same thing (72 per inch). As monitors became more dense (but before retina) this approached 96 and then 130.
If you've got a Linux workstation handy, try manually setting your x86 DPI to match your monitor's specs. Everything will look giant because most apps are written assuming DPI is an arbitrary constant (75 or 96), but most people use monitors that are more dense than that.
When you set your DPI to be its actual value, you'll realize that people have become accustomed to screens being more dense over time, but there was certainly a time when DPIs in the 70s were considered par for the course. In fact, many older people prefer less dense pixels because it's easier for them to see bigger things.
You're right about the importance that distance from the screen plays, but in my experience, a 27-28" 1080p monitor (of which there are quite a few on the market) would have to sit too far away to use for anything but movie viewing and gaming.
Non-Retina MacBooks start at 110 PPI. Cinema Displays have hovered around 100 PPI for about a decade, with the 27” Thunderbolt Display topping out at 109 PPI (same for its sister 27” iMac).
At 28", a 3840 x 2160 panel has a PPI of 157, which, dividing by two to get the equivalent non-Retina PPI, comes to only 78.5, a reduction of over 20% from the lowest-PPI Cinema Displays. This means, on a Mac in Retina mode, everything in the UI will be 20% bigger than normal. Maybe that’s something you could get used to, but it’s far from the much more optimal 24” panel, with a PPI of 184 (92 PPI non-Retina, very close to a 24” Cinema Display).