I'm not sure Mellanox is "favoriting" iser over srp as a principle, It's just that iser is more scalable and more robust then srp within ConnectX-3 product.
Correct. currently only mlnx-NATIVE-ESXi6.0-ConnectX-4 ETH Driver is available and no VPi/IB support is scheduled for the near future.
suggesting to post our website from time to time and get updated on the product release