Scott has been getting tons of questions lately on whether people should buy a 4K TV. Scott says that they're not even out yet, but sure, if you can afford the $25-40,000 price tag! The Sony 4K TV costs $25K, and comes with a nice video server and 10 blu-ray quality movies loaded on. Sony also plans to update that server with more movies.
The real question is, will you even see the difference? There's a qualitative difference, sure, but many say that the human eye really can't see the difference unless the TV size approaches 70", which is very expensive. Then there's the size of optical discs would have to be to store the digital information for a 4K movie. BDXL promises to bring 100GB of space on four layers of a blu-ray disc, but it's only burnable right now.
RED is coming out with the REDRay player, which will be able to stream 4K content to a 4K display. Although, then 4K content will have a significant impact on bandwidth.