I just run on a 45" TV at 3840 x 2160. Sure, the response time is slow for gaming, but it works fine for movies and coding. And I have enough space that I can set each window to whatever size and orientation I want.
Previously dual monitor, 24" 1920 x 1080, portrait left, landscape right. left was usually for email and chat, right for coding and browser.
Now it's a single 40" 4k tv as my display. Using gridmove to easily partition the screen as needed. It's like have 4 1080p screens with no border. Only downside I've come across is some screensharing apps will always share the entire desktop when sharing a single app (webex is worst offender) - just the app window will be shown, but with massive greyed out background. Can be fixed by changing desktop res, just an annoyance.
Moving to a single massive screen has honestly lead to better productivity, but i possibly attribute that more to gridmove than overall screen real estate.