Never did an In place upgrade on PVS servers. Also stood up new Servers.
My steps I do as follows.
1. Stand up new Servers, ( do all the basic Domain/Security stuff)
2. Add same version of PVS software.
3. Join new servers to existing farm.
4. Copy vDisk over to the new PVS server, make sure replication shows good.
5. If using NS to load balance them, Add them in the backend. If not, Update the BDM Side of things.
6. Take a test Target, and stream it from the new Servers, ensure things are good.
If you decide to do the Inplace server upgrade. I would snapshot it, remove the PVS software. Upgrade it, ensure the OS is healthy, Reinstall the PVS software, joining to exiting farm. Test Streaming, and then add back into the mix