Windows 8.1 already offers support for resolutions up to 4K, but the Windows 9 release is said to take things to the next level, adding support for 8K resolutions and improved DPI scaling. This was discovered in the leaked Windows 9 build 9832.
DPI scaling will also be better now, as shown by the leaks included here. We had indications that technology was going to evolve in that direction recently, as Dell launched the UltraSharp 27 Ultra HD 5K Monitor, with a resolution of 5120 x 2880 pixels. It’s basically the equivalent of 4 times the resolution of QHD and 7 times the resolution of Full HD. If you ever used a very high resolution screen with Windows 8, you probably know that the OS had problem with high DPI devices.
Windows 8.1 solved some problems, but the developers didn’t get much love in that area. Last we heard there was a Windows 9 event schduled for September 30th in San Francisco and we also learned that the Start menu will change color to match the theme of the desktop. Expect more early builds to leak more details over the following week or so!