Looks like they just posted an update on the site, as of 10/17:
Next Steps - as of 10/17/2011
Last week we registered everyone into the Connect Site to get you "onboarded" to the program, but there are still several steps to go to get you fully up and running and we will be communicating that to you over the next week or so.
We still need to do the administrative work to get your GamerTag registered to the Private Forums and of course provide you with the instructions on how to register your Console(s). Those details are coming out very soon, until then, know that you are "IN" for the Fall 2011 Xbox LIVE Update Preview program and we are ecstatic to have you on board!
Frequently Asked Questions:
Q. Can I tell others that I am in the Xbox LIVE Update Preview Program?
A. Yes, you can tell people you are in, but sharing specific information about the program is a violation of the program agreement.
Q. When do I register my console information?
A. Soon, we will provide the instructions on how to register your console as soon as our administrative steps are done on our side. Look for updates via this portal.
Q. I provided incorrect information in the registration survey, can I fix it?
A. We will provide you an opportunity to update critical information such as your GamerTag details (gets you access to the Private Forums) in the next day or so, all other information is used for analysis purposes on our end and should not impact your ability to participate in the program.