Well everything is in the title, no?
OLED for « Organic Light-Emitting Diode ». The OLED technology is full of promises: Lower cost in the future (when mass production will start), Light weight, flexible screen, wider viewing angles, improved brightness, better response time (for a good fluidity in the mouvements)…
4K or Ultra HD, provides an image that is 4 times more accurate than HD, imagine a movie in 3840 × 2160 resolution?
Sony and his partner Panasonic are working on it. While Sony offers a variety of devices needed for all the movie production, it will be surely one of the first brand to offer such a television for mass market.
Maybe Christmas 2013 if Sony and his partner are able to resolve some technical issues.
Source wikipedia OLED.
Source wikipedia 4K.
Tokyo Dn'U 