Hold on to your hats, patch 3.0.1 is now up on the background downloader, and Zarhym wasn't kidding at all when he said it was going to be big. 821MB to be exact.
So, you may want to get started now with the download! As a reminder, you can choose to have the downloader running in multiple ways: while you're playing, when you exit WoW, or both.
And here's a screen cap of the downloader, just to prove it's actually available! If you haven't started your launcher in a while, you may want to so you can grab this patch ahead of time. Don't wait until patch day!
Thanks to Levicen for the heads up!