I'm flirting with the idea of going to dual 4k or 5k screens at home some time this year though, because I think that might be a better setup for working with UE4 or Unity than what I've got now. I would think that 3 or more widescreen displays laid out horizontally would be too much head-swivel to be comfortable or useful, unless maybe they were in portrait orientation.
I have a single 40" 4K display at the moment (one of the S. Korean eBay specials), and I'd agree. No way to get a 2nd one (god forbid a 3rd) in horizontal.
I am flirting the idea with getting a wider aspect-ratio display with matching horizontal resolution. Say, 3840x1440, and mounting it directly *above* the current display, angled downwards. I think that's a better use of space, and looking up is arguably better ergonomically than swiveling...