Apparently this is posted on the EU Site: http://eu.battle.net/faq/index.html
This info is not listed on the US site.
Q: What happens if I don’t merge my World of Warcraft account with a Battle.net account?
A: After November 12, 2009, you won’t be able to log in to the game unless you merge your account with a Battle.net account. You will need to log in using your Battle.net account username (your email address) and password.
Q: How can I obtain the penguin pet?
A: Once you’ve successfully merged a World of Warcraft account with a Battle.net account, the penguin pet will be sent via in-game mail to all existing characters on the merged World of Warcraft account, along with all future characters on that World of Warcraft account. Players who merged previously will also receive the pet this way.
Q: Do I need to merge by a certain date in order to receive the penguin?
A: We plan to remove the ability to get the penguin pet at some point in the future, we haven’t determined exactly when just yet.
Q: If I create a new World of Warcraft account, will I receive the pet?
A: Only existing World of Warcraft accounts that merge with a Battle.net account are eligible to receive the penguin pet. If you create a new Battle.net account after November 11 and merge an existing World of Warcraft account with it you will still be able to receive the pet. However, please note that we plan to remove the ability to get the penguin pet at some point in the future.