I have edited the "Your copyright" section to make note that there are a few varying licenses and that new and the majority of wikis use CC-BY-SA. I'm not sure the copyright help page requires a whole section discussing the license varaints.
The first section of the licensing page also specifies that unless the footer says otherwise, the content is CC-BY-SA:
"Except where otherwise specified, the text on Wikia sites is licensed under the Creative Commons Attribution-Share Alike License 3.0 (Unported) (CC-BY-SA).
Some wikis use licenses other than the CC-BY-SA license. The license used by an individual wiki is made clear in the footer and/or on the edit page of that wiki."