Tomorrow -- that's Tuesday, September 10th -- U.S. realms will be going offline for maintenance at midnight, Pacific time and are scheduled to come back up by 10 in the morning. This downtime is, of course, for the launch of patch 5.4
: so by tomorrow afternoon the Siege of Orgrimmar should be upon us. We think the schedule is on the optimistic side for a patch roll-out, but here at WoW Insider, we'll keep our fingers crossed for servers popping back online quickly so we can all get back to gaming.
Not sure what all the fuss is about? Blizzard posted a roundup of patch 5.4 info
to catch you up on all the news, but if you need to go more basic than that you can also check our rookie writeup on what WoW patches are