I am able to run a Windows 7 VM at full native resolution on a iMac with a Retina 5K display (HiDPI / Retina, at 5120 x 2880) using VMware Fusion 7.
Windows 8.1, though, does not list any resolution greater than 2560 x 1920. This happens despite having selected the "Use full resolution for Retina display" option in VMware Fusion 7. I have also reinstalled the VMware tools multiple times (that seemed to help in an unrelated Windows XP resolution issue) and tweaked the VMX configuration values -- I even tried to match the values to those found in the Windows 7 VM's VMX. Nothing has worked.
For all I know, VMware may be supporting the native resolution, and it just doesn't show in the Windows 8 "Screen Resolution"'s list of resolutions. I did not find a way to override the list of available resolutions in Windows 8, so I was unable to test that hypothesis.
Has anyone managed to run a Windows 8(.1) VM at 5120 x 2880? In VMware Fusion 7? Any ideas on how to solve this?