Sony has just listed an 4K TV on their site. it's 84", and it costs $24,999.99 (apparently that pricing trick of dropping a penny to rounding down one of the left-side figures matters even when you're talking about spending the price of a Prius on a television). This is the same list price as the one for their "consumer" 4K projector which is already on the market.
I'm excited for the future of 4K entertainment, but you are almost beyond an early adopter to jump on this bandwagon so soon. That's because for consumers there is almost no 4K content that you could even send to this display.
I say almost because there is one movie I'm aware of that's available for purchase in 4K resolution: TimeScapes. You can grab a quick preview of a 2560p clip from TimeScapes here (right click the link and hit save as; you really don't want to try to play it in your browser). You can purchase either a 25Gb 4K file of TimeScapes on a USB stick for $99.95 or a 330Gb 4K 12 bit Cineform file on a hard drive for $299.95. And then you'll need a 4K video card in your computer to even push that file to your new 4K TV to turn it into the world's largest, sharpest nature screensaver display.
Red announced a Red Ray device which is their delivery solution for 4K content files, but it has yet to receive a release date. They also announced their own 4K projector and have demoed it here and there, but again there's no official ship date yet.
Is this all absurd? I suppose. But who am I kidding? I can't wait to go 4K.
UPDATE: If you have just $20,000 burning a hole in your pocket instead of $25,000, then this LG 4K TV, also 84", may be more your speed. Given that both the Sony and LG are 84", they may be sharing the same source for the display.