If there is a widely accepted standard, there is a guaranteed customer base. 4K is the next logical plateau since it is gaining traction as the next broadcast standard (although NHK is pushing for 8K!).
There are only two suppliers of flat panels, Samsung and Sharp (and Sharp isn't looking good financially). If you ask them to make a common, but not wildly common resolution, it will cost much more.
In two years, you will be able to buy a 4K monitor for the same price as a 1080p screen, and all new video cards will support it.
Any circuit design must contain at least one part which is obsolete, two parts which are unobtainable, and three parts which are still under development.