For a few years I used a 34" ultrawide next to a 27" monitor (they're exactly the same height).

Recently I switched to a single 38" ultrawide (a xr382cqk) and I've taken down the second monitor.

Windows and OS X both have good enough tiling that I can use the single monitor without the distraction of bezels, and there's much less ceremony to hooking up one monitor

I think the same thing would work with a ~40" TV, and I e seen people do it, I just prefer the space efficiency of the ultrawide