Update: Apparently it's not going as smoothly as they would like! Here's the quote from Wii U community manager A_Trey_U:
Hello Wii U Community,
We are noticing some issues with the version of the patch that was posted that you guys are also reporting here on the forums. We are working with Nintendo on a resolution to this problem and hope to know more at some point tomorrow. I will keep you posted as I receive more information.
We are aware that some of the menu listings from the 360's Revolution DLC drop are showing up in the game. This is not a confirmation of DLC for the Wii U, just a versioning problem that we are working to address.
I do not want to publish the list of known fixes until I have confirmation that they are all live. I hope to be able to do this tomorrow, but as I mentioned, this is something we are working on with Nintendo, so the timeline isn't entirely in our hands.
Thank you for understanding.
No details on what it does other than bringing the Wii U "up to date" with the PS3 and 360, but I just wanted to let everyone know that it is live and you can go download it right now. I haven't noticed any explicit change yet, and we won't be getting the full details list for a little while now.
Via Call of Duty Community