4k TV's worth it?

[ahoragi]

So I have a P50ST50 50" 3D Plasma TV that's been doing just fine. It's kinda eye-straining with gaming but is great with TV and movies. I'm seeing all these 4k UHD TV's at the stores and a bit tempted. I paid over a grand for my 50" 3D tv and these 4k 55-65 inch tv's are going for half the price and reviews are very good. There's a 55" Samsung 4K Smart TV on sale for $399. That's insane.

I don't have 4k cable (Just HD box) or a 4k blu ray player so would they be worth buying?

I wanna go bigger in my living room and move the 3D tv to my computer/tech room. I'm also trying to prepare for the release of Avatar 2 in whatever viewing format it will be released in. I want to get the full experience in my living room.