Wikia has released a tentative schedule for the release of the new skin, and say that the end of the public and private beta will end soon. Basically we have only about 5 weeks left to enjoy the Monaco skin. Sannse posted it on her blog here. The new skin, which is still a piece of junk IMHO, will start to be implemented in the coming weeks with October 20, 2010 being the official implantation date for the new skin. After that, users will still have the option to edit in Monaco, but that option will go away on November 3, 2010, so just over 5 weeks to enjoy the useful and frankly much better skin. You can see the full schedule along with update on the blog linked above.
In my opinion, Wikia is making a terrible mistake and will lead to many people leaving. I won't go anywhere, but I'll still hate the new skin.
Oh and about how long the "beta" lasted, just about one week. That isn't a lot of time to gather comments and act on them, no matter what you are doing.