A few sources have come up stating that the new dashboard update for the Xbox 360 announced at this year's E3 will launch this November. First, RPG-TV managed to get a preview of the new Xbox experience at Microsoft's London office;
"I'm not sure if this has been confirmed already or not but I was told the new dashboard would arrive in November."
Also, in the latest issue of Official Xbox Magazine (pg. 64 & 67) there is a preview of the update and they mention that "come November, Microsoft's biggest 360 gambit since the launch itself will be shared with -- and judged by -- the public at large," as well as "questions may remain unanswered until November" all but confirming with the company that the new software will drop then.
It is still to be seen whether November will be the month, but more and more signs are pointing to the New Xbox Experience launching along side your Thanksgiving dinner.