So the Wrath of the Lich King beta started, making it likely that the expansion will come out before christmas. If you haven't "opted in" to the beta yet, you should do that on your World of Warcraft account page. Log in your account as normal, scroll down to the last option, and there should be the WotLK beta opt-in, which is free. Then you still need to wait for an e-mail to invite you. I haven't got one yet.
What I did get was a FAKE WotLK beta invite, but I didn't fall for it, as it lead to a site with a .tk domain. Be very, very careful of those. They lead you to a fake account login screen, and when you enter your userID and password there, you'll find all your characters stripped naked the next day, if not deleted. Do not enter your userID and password on any site which isn't https, for a safe connection, and is www.worldofwarcraft.com, or www.wow-europe.com.
I haven't entered my WWI code for "one future Blizzard beta" yet, because when I got it the codes weren't working yet. But even with the code one doesn't necessarily get WotLK beta access. What I *could* enter now that patch 2.4.3 is out is my code for the Tyrael pet, so now my priest has a somewhat chubby angel floating behind him. Cute!