Heck, my $100 non-Apple phone has a ~330 ppi display, same as a "retina" iPhone. And high-res displays (especially from Korea) have plummeted in price. https://news.ycombinator.com/item?id=4292450 High-DPI won't be a niche for long.
Those two are not the same thing at all; a 27" 2560x1440 like the one you link to is ~108dpi.
According to Apple's math for "Retina", phones are held at 10" and you need 330ppi like an iPhone. But laptop screens are used at 16" and only need 220ppi like the new Retina MacBooks. So if you use a monitor at a distance of 30" (which is more likely if you use a huge 27" monitor) then you only need about 120ppi to have the same angular resolution. I've seen one of those Korean monitors, and they're definitely dense enough that you need to increase the size of elements on the display. That means pixelization unless you use high-res assets.
Good to know. Got schooled on angular resolution today :)