Thanks for the information. Based on this article it looks like a driver upgrade will allow my HD4000 to use 4k: New Intel HD 3000 and HD 4000 Drivers: Support for Windows 8, 4k Ultra HD, OpenGL 4.0, and More « UltrabookNews, Reviews and the Ultrabook Database
In addition to some game-specific performance updates, Intel has also enabled 4k Ultra HD video output and OpenGL 4.0 for Ivy Bridge / HD 4000, as well as OpenCL 1.1 for Sandy Bridge / HD 3000. All Ultrabook users should update, even if your Ultrabook has discrete graphics!