The pre-order is now live. You can get your character boost and pre-order Warlords of Draenor.
We've been getting a lot of tips that the Warlords of Draenor pre-orders are being prepped for, and based on our own excursions to the Account Management page of Battle.net, it seems to be the case - there's the little icon in the corner there (with perhaps our first view of the box art for Warlords of Draenor) waiting for us to click on it. Doing so doesn't allow you to pre-order as of this writing, however.
Based on this and the cinematic from Sunday morning, it seems like pre-orders and the level 90 boost are imminent. We'll be keeping an eye on this and if and when they come online we'll inform you.