At MWC in Barcelona, LG has demonstrated Ultra HD streaming from a phone to an Ultra HD TV via Miracast. It is a prototype technology for now.
Ultra HD streaming from smartphone to TV
LG demonstrated how they can take a smartphone and stream Ultra HD (4K) content onto its 84-inch Ultra HD TV. The demonstration involved some upscaling as the phone ran a game in 1080p resolution but upscaled to Ultra HD before the signal hit the TV.

LG demonstrates Ultra HD streaming from smartphone to TV
The streaming technology is powered by Miracast; Android’s pendant to Airplay. Miracast has found its way into a range of new Android smartphones and tablet as well as new TVs. When both devices support Miracast users can stream media files or games from the handheld device to the big screen. However, this is the first time it has been demonstrated with Ultra HD resolution.
The demonstration shows how powerful mobile devices are becoming and how they can integrate with the living room TVs, possibly even acting as game consoles or media players.