Inside the Factory have announced that the wiki help for Revit 2012 is now live and can be accessed via the following url: http://wikihelp.autodesk.com/Revit/enu/2012
Which means you can get a look at What's New in 2012 and read up before being able to download. Autodesk never like to give an actual download date, but we all know its going to be sometime within the next 10 days. They always follow the same patten each year.
So go and take a look.....