The panel is still a basic TN one with a CCFL or LED backlit option.
If you are referering to OLEDs then yes, they are superior to both LCDs and Plasmas.
I vaguely remember seeing a prototype of a LED tv too but that was so expensive that it made the 1L 11" Sony OLED look cheap in comparison.
plasmas (perhaps) require more R&D, and tend to last longer than LEDs/LED-LCDs. manufacturers in these times are not surely looking forward to sell something that would last long to a customer. as sarath said, other TVs can be produced with lesser input to gain high output.
Plasmas have a lower life than LCDs do. This was marketed heavily but the problem is no one calculated the real life scenario.
For example, a crude one, take a LCD which lasts 5 times as long as a Plasma. Now let the Plasma have a life of 5 years. Which makes the LCD last 25. Now in real life for a TV to make it through 5 years or more is a tough call. So practically speaking, even if the LCD lasts endlessly on paper, in real life it may not last that long especially with leaps in resolution and such.
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Ghosmanas has a plasma and I don't think he would ever buy a TN LCD panel for TV viewing after it.