Blizzard has added two test realms which are currently running the latest patch. There's no word yet when that patch will go to the live servers, though presumably not soon as it obviously needs to be tested out. Invitations will be going out to selected level 55 to 60 characters to ask if they want to copy their characters over to the test realms and play under the newest version. The patch looks enormous. Grab a cup of coffee or other beverage of choice before starting to read through all of the notes. The official post regarding the test server can be found on the main site, along with the patch notes and test realm faq.