Cable providers can barely provide 1080 resolution, 4k is a long way from being practical. Game developers aren't going to be crazy about it, either...720p is still pretty much the standard for a lot of them.

It's not a pipe dream if you have a capable PC, or want a solution that can display both 720p and 1080p without any scaling artifacts. Also a good solution to get rid of the screendoor effect on projectors.

4K tv is indeed a pipe dream, 4K movies are coming next year.
http://www.theverge.com/2013/11/2/5058386/netflix-testing-ultra-hd-4k-to-prepare-for-launch-next-year
http://www.reddit.com/r/technology/comments/1pp45i/4k_streaming_is_here_netflix_has_added_short_8/

Right now is still a bit early, wait until 4K tvs support 2160p60 (hdmi 2.0) but if you can't wait, Sony aready has a 4K streaming service
https://store.sony.com/4k-ultra-hd-media-player-zid27-FMPX1/cat-27-catid-All-Internet-Players
http://www.digitaltrends.com/home-theater/sony-launches-4k-video-unlimited-download-service-with-70-titles/

A 24-hour TV show rental will cost $4.00, whereas a 24-hour movie rental comes in at $8.00. Movie purchases will cost $30.00 and include an UltraViolet digital copy for use with portable media devices. According to a Sony representative, a 2-hour 4K movie download will eat up about 40 GB of storage. With 2 TB of storage on board, the FMP-X1 can hold approximately 50 movies, though its capacity can be expanded with an external hard drive.

I rather wait for a disc based solution, 40Gb for a movie is hardly better then 1080p blu-ray quality. They will switch to H.265 encoding that nearly doubles compression efficiency of h.264, but it seems they want to reduce file size for streaming first instead of improving quality.