depends on who you believe.

http://nvonews.com/2011/12/20/apple-ipad-3-ipad-mini-release-expected-soon-with-new-specs/ towards end of year?
http://www.inc.com/john-brandon/ipad-3-coming-in-early-2012-release-date-and-spec-rumors.html early 2012
http://www.ipad3releasedates.net/ iPad 2+ coming before iPad 3 then later 2012?
http://www.techradar.com/news/mobile-computing/tablets/ipad-3-rumours-what-you-need-to-know-937498 spring 2012
http://www.ipad3-release.com/2011/production-of-ipad-3-to-start-in-january-digitimes-reports/ starting production in January ?

My prediction, sometime in either 2012 or 2013 probably unless they don't. And you can hold me to that.