We can now confirm that the XB360 Fall dashboard update is not going to be live after today's update as was originally rumored. This confirmation comes from Major Nelson, who mentioned the downtime is in preperation for Halo 3 instead.

We are not sure of the date of the Fall dashboard, but it is expected sometime before the end of October.

The second we find out more, so will you. Stay tuned!

Source:
http://www.majornelson.com/