If you turn on your 360 today and head over to the 'Spotlight' section of your dashboard you will notice an advertisement for the "$50 mail in rebate" for the the Xbox 360 Elite. Clicking upon thid you will be able to read the details of the deal and what the Xbox 360 Elite has to offer. If you scroll down and look under the *Xbox Live Gold membership are you will see that it clearly states "Facebook and Twitter coming November 2009".
So there you have it. Facebook and Twitter are coming in November and it is confirmed by Microsoft. Well, sort of. ;)