As of today, the patch data is available to us in the Background Downloader. There are multiple sections to this data around 4.68 gigs each. Each takes around 45 minutes to an hour to download fully while not running WoW; once the first section is [Finished] you must re-open the .exe file to continue. I would like to thank SuicidalZebra for pointing out my flaw!
If you need help running the program, here is how to find and run it in Windows Vista:
– (My) Computer -> C:
– User -> Public -> Games
– World of Warcraft
See, easy as pie! The fact that this data is available and the blue post announcing extended maintenance tomorrow, strongly implies tomorrow is patch day! I hope to be able to provide a 4.0.1 guide, but I cannot guarantee at this moment when it will be available. Also remember to do anything with your current currency should you chose to do so! Good luck and hope to see you around tomorrow for Tuesday!