This is mostly exactly the current question I am trying to answer for myself.
We have a few ESXi hosts currently on v5.5 with dual port VPI adapters.
We want to run SRP/iSER on one port back to our SAN and we want to run IPoIB on the other port for vMotion communications.
We don't want to go to Ethernet based adapters and/or have to buy managed switches to achieve this.
Ultimately we don't want to implement this and then find it won't run of v6.x either so forwards compatibility is important also.