You don't need to "route" iSCSI traffic to use VLAN's. Just create a Virtual Machine Port Group on the same VLAN as iSCSI and you will be good to go!
vSwitch 0
VM Network
- VM1
- VM2
- VM3
Management Network
- vmk0: 192.168.10.10
vSwitch 1
VMkernel-iSCSI-01 (VLAN 999)
- vmk1: 192.168.20.10
VMkernel-iSCSI-02 (VLAN 999)
- vmk2: 192.168.20.11
VM Network 2 (VLAN 999)
- VM3
In this example, VM3 is multi-homed on both VM Network and VM Network 2 (be sure to set a gateway only on the production network, not the iSCSI network), and you will be able to use VM3 to manage the SAN.
Remember, using VLAN's with iSCSI costs you 4 bytes a frame, so be sure to use Jumbos if you can - and don't forget to do port binding if you use more than one iSCSI VMkernel.