The key to more successful large screen displays will be to make them even wider, but not taller. Your field of view is about 160-180 degrees wide laterally, of about which 130 degrees are stereoscopic. It's only about 120 degrees vertically, most of which is stereoscopic on the vertical axis. But it's a funny thing, the field of view is somewhat de-centered vertically: It typically extends about 45-50 degrees vertically above centre, and 65-75 degrees below.
Check it out:
NASA explains here
What this means for displays is that:
We don't like to look up - one reason why good ergonomic practice suggests aligning the top of your monitor with your sight-line.
We like a centre (stereoscopic) sweet spot of about 120 x 90 or 100 degrees. There's more stereoscopic field, but it's mostly useful for seeing what our hands and feet are doing. Useful for running away from big things that can eat us and not tripping over rocks, or for picking our small things we can eat while not tripping over rocks. There's also lots more monoscopic field horizontally at the outer edges - mostly useful for detecting big things in our periphery trying to sneak up beside us and eat us. Also informative for computer displays: line up the top, because the tendency is to look down over the image. Also explains the choice of historic 12:9 and 12:10 formats (4:3 an 5:4) and contemporary 16:10 and 16:9.
Now, you can have bigger and taller displays but you have to move back a bit to make it comfortable. You lose some of that cozy feeling when that happens. Desks, chairs, and practical space limits a sensible display choice to something viewed comfortably within a 2 to 4 foot distance. Probably not something immersive, but that sits in the sweet spot for vision without being fatiguing. Normally, this wouldn't recommend an even larger display, not wider or taller. But I think wider would work as a better dual screen alternative. a 21:9 would give essentially two 5:4 displays, but no seam.
Using the same height as the current 27" 16:9, you get a 33" 21:9 monitor. Certainly something interesting to sell at the high end of the cinema display line. Now if you use the same height as the old 30" display, you get a whopping 40" desktop display, but neither would be any taller than any monitor apple has ever sold.
Apple needs a monitor to go with their Mac Pro workstations. They could charge virtually anything for a 33 to 40" 4K ultra-wide monitor and the people who need them would pay.