WoW Insider has a few sources that are all pointing towards tomorrow as the release date, save some major internal mess up at Blizzard HQ. MMO-Champion also has some (Are our sources the same? The world may never know.), and Bibi is running a similar announcement over there. While these are, by definition, just rumors, they are taken quite credibly by many of us.
What does this mean for you?
It means you'll want to become familiar quickly with all the patch 3.1 changes if you haven't already. The best place to find out everything is via WoW Insider's Guide to Patch 3.1. Be sure to check back on it throughout this evening as we get more information in and tomorrow as the floodgates open.
Should be a fun few days!