It does support higher resolutions.
Like Pook, I run a 3 monitor setup at higher resolution.
My only comment is that the hotbars do not scale with resolution.
Sitting 3ft away at a computer is not too bad.
But if you go with a 50" tv, you're going to need to be at 6-7" away from the screen to avoid eye fatigue and not see all the pixels (assuming 1080p).
At that distance, text and the hotbar boxes can get very hard to see/read. If the resolution is 1080, then take a screenshot of DDO at that resolution on a USB stick with you, plug it in and try viewing it from where you think you'll be sitting.
I once tried playing it on a standard 1080i res 65" TV and it wasn't very good for me.
If you're a minimalist, or you can remember the shortcut keys for all 200 hotbar slots - you're golden.

If you go with a TV, understand the specs.
True 4K (DCI) is 1.9:1 and will make the game look a little stretched.
Most consumer TV's seem to be UHD-1 which is 3840x2160 (the more common ratio of 1.78:1).