I think you totally misunderstood the Zentyal roadmap. The goal is to implement on server side Single Sign On and Domain Controller for both operating systems Windows (with Samba4) and Linux (with Kerberos). Actually, with Samba4 you get a full drop-in Microsoft Domain Controller replacement (advanced policies, etc.), something that is not present on the Linux world. That's one the things will implement Zentyal Desktop for Linux. To give you an example, on Zentyal server you will able to define a policy: "apply this wallpaper to all the workstations", on Windows will be implemented via policy with Samba4, on Linux will be implemented via Zentyal Desktop.
Zentyal Desktop will preconfigure some applications, do some monitoring, alerts, etc. Will be available for both Windows and Linux, with different features (policies are already implemented on Windows, not on Linux), will ease the configuration and management of desktops. If the desktop is VDI, Thin Client (LTSP, TCOS, etc), Fat Client or bare metal, doesn't mind.
About VDI which seems you are very interested into, I suggested you some time ago how to put some configuration snippets inside /etc/zentyal/dhcp so you could integrate these options you need for VDI with the Zentyal interface management. Give it a try. If VDI become a common deployment in the community, I'm completely sure that these options will come to the web interface too!