One company that I'm going to keep an eye out on is Pluribus Networks . They have the byline "Virtualization without Limits". Sunay Tripathi , one of the founders, is also of the driving forces behind the Solaris 10 TCP stack rewrite, and Crossbow, the network virtualization in the opensolaris kernel (and part of the upcoming Solaris 11).
Sunay recently blogged about "Network 2.0: Virtualization without limits", where he's written about a Network OS that controlls all switches, treating the network "exactly as one giant resource pool".
Pluribus are quiet about what they're doing, but Sunay has said that they "a network hypervisor that has semantics similar to a tight coupled cluster but controls a collection of switches and scales from one instance to hundred plus instances".
This is purely speculation on my part, but I do wonder if OpenVSwitch would be the management layer, or perhaps integrate/interoperate with Pluribus' NetVizor.
In any case, the future does look exciting :)