I decided to try to upgrade my Windows 8.1 VM to Windows 10, even though I already have a Windows 10 VM. I just wanted to see if it would work or not. When I clicked the upgrade button from the System Tray it came back and said it couldn't upgrade due to the VMware SVGA 3D driver.
I did some looking around on the VMware forums and found this simple process to make the upgrade work.
I followed several things in that thread, linked above, and none worked for me until I got to this process. It worked like a charm and the upgrade is proceeding right now.
Disclaimer: This particular installation of Windows 8.1 was a conversion from Apple Boot Camp to Fusion 7 last year when Fusion 7 was released. Not that it has much, if any, impact on this upgrade process.
Download the pdf version with pictures here.