I bought a Samsung UN65HU8550 a few months ago. I will never go back. Its picture quality still startles me whenever I turn it on. Its upconversion to 4K is uncanny. I am still exploring its exceptionally rich set of advanced features. The black levels make the whole TV disappear in a dark room when the screen goes black. I get no noticeable motion blur. The (active) 3D is the most accurate and realistic I have ever seen, even in a high-tech, high framing rate iMax theater -- no ghosting at all.
It is spectacular. Utterly spectacular. And it uses WAY less juice than any plasma.
And it is nice that some native 4K content is beginning to come out on pay services. "Breaking Bad" on Netflix is an immersive experience that enters into your nightmares. It's like looking through an open window at the action.
Plasma is likely going away. 1080i and 1080p probably won't for awhile because of bandwidth and disk capacity issues. Although there are now some higher resolution sets available, I do not imagine that they will ever be worth the price over 4K, which has now very nearly hit the human eye's capacity to perceive detail. The next thing will be OLED, and the price is dropping rapidly now (although still stratospheric) but OLED offers advantages beyond backlit LED or other designs, notably its infinite contrast ratio, extremely low power consumption, and the ability to be made very thin, lightweight and flexible, so they could be rolled up like a projector screen or taped to the wall like a poster. They're coming, but not really quite here yet.
But I think 4K is here to stay for many, many years.