You tell me what you want.  The cabanas are your time.  What topics do you want to cover?  I think it is natural to bring in the speakers after their session, but what else is interesting?  Who do you want to hear from?  What do you want to hear about?  John Bristowe and Aaron Skonnard are already planning BOFs.  I can imagine following the BOF up with a whiteboard sessions the next day in the cabana.  One is on WSE another on Contract first.  What do you want to hear about in the cabanna?

Implementing WS-RM, SAML, Custom Issuing services, Eventing, BA, with WSE?

Indigo Programming

UDDI

Discovering services

Extending VSTS to generate new types of code

WSDL editing and code gen