Correct people are commenting on the location of the donation tab by the looks of it
http://www.neowin.net/news/wikipedia-starts-accepting-bitcoins-earns-140000-profit-in-the-first-week
https://bitcointalk.org/index.php?topic=731970.0

https://donate.wikimedia.org/w/index.php?title=Special:FundraiserLandingPage&country=CA&uselang=en&utm_medium=sidebar&utm_source=donate&utm_campaign=C13_en.wikipedia.org

Aka Bitcoin is listed under other ways to give right now not main page.
https://wikimediafoundation.org/wiki/Ways_to_Give/en