There are many barriers to 4K display adoption. For televisions, 4K only makes sense for consumers if four major criteria are met: content needs to be shot in 4K, edited in that resolution, broadcast or delivered in a mainstream format, and finally, the televisions themselves have to be affordable. Content providers like Netflix are working to solve the first of those three criteria--eg. with its House of Cards Season 2--and it'll be a year or two until 4K TVs come down dramatically in price. Or maybe not. This week, both Vizio and Polaroid announced 50-inch 4K televisions for $1000, well below what LG and Samsung have been pricing their Ultra HD sets. From reports, Vizio's 4K TV looks more promising in terms of image quality, though there are many unknowns such as refresh rate and input options.
On the PC side, desktop operating systems and web content can scale to whatever resolution a monitor supports, so 4K adoption there is a more a factor of price. Dell's 28-inch Ultrasharp P2815Q monitor was just confirmed for $700, well below the sub-$1000 promise that Dell made late last year. That's an incredibly attractive price for a 3840x2160 resolution display, and may get me to trade-up from my current 30-inch 1600p monitor.