Traffic is Seperated by using a different VLAN. Yes it does travel over the same uplink, but VLAN's are widely used as a way of Sperating Traffic.

As long as the Service Console and vMotion Port Groups have different VLAN IDs then the traffic cannot get from one VLAN to another.

This is used widely. For example if you have a Cisco Network with 10 Physical Switches using VLANS, you will always have trunks between these switches that are sending traffic for all different VLANS. However the Data is Tagged with a VLAN ID.

Using a network standard called 802.1Q or VLAN Tagging, this "allows multiple bridged networks to transparently share the same physical network link without leakage of information between networks".

(source: )

I believe that this is your best option if you require a redundancy and failover.

Steve