It also notes that an "audio change" in said software will not allow participants to use individual or party chat with anyone that is not part of the preview program. This could indicate that participants will be trying out the new Kinect dashboard seen at E3, which featured a new video chat application.
The email address attached to the invites appears to be valid, and it's worth pointing out that Microsoft has used Connect in the past, notably before it launched the NXE. Microsoft has yet to respond to Joystiq's inquiries into the validity of the invitation.
[Thanks to everyone that sent this in!]