Patch 6.0.2 - coming to a downloader near you ...

Blizzard has announced:

To help you get prepared for the upcoming Warlords of Draenor Patch 6.0.2 release, we’ve uploaded the patch data to the background downloader. By downloading the patch in advance, you’ll be ready to get in-game and start playing as soon as the expansion goes live!

This is already showing as about to download on my launcher.

More information can be found about this here.