vSwitch

VMware open development of ESX Virtual Switches to Third Party vendors, and Cisco is expected to be the first company announcing such product, perhaps Virtual Catalyst?

You must read this and this.

"A virtual switch, vSwitch, works much like a physical Ethernet switch. It detects which virtual machines are logically connected to each of its virtual ports and uses that information to forward traffic to the correct virtual machines. A vSwitch can be connected to physical switches using physical Ethernet adapters, also referred to as uplink adapters, to join virtual networks with physical networks. This type of connection is similar to connecting physical switches together to create a larger network. Even though a vSwitch works much like a physical switch, it does not have some of the advanced functionality of a physical switch. For more information on vSwitches"

To me, again it will be a new security issue of course. We'll see...