Two upgrade flows are available (and supported) for RHEV 3.6 to RHV 4.0, and must be documented:
1. Standard (bare metal) RHEV 3.6 Manager to standard (bare metal) RHV 4.0 Manager
2. Self-hosted RHEV 3.6 Manager to self-hosted RHV 4.0 Manager
See bug 1318580 for more details on flow 1. Flow 2 is proposed in bug 1319457, but should be confirmed with engineering and QE.
NOTE: In RHV 4.0, self-hosted engine setup is supported using the RHEV-M Virtual Appliance only.