In case you are have difficulty with accessing the link I provided, the following excerpt from that article helps to answer your question.
"On April 2, 2012, the National Archives (NARA) will provide access to the images of the 1940 U.S. Census for the first time. Upon its release, FamilySearch and many top genealogy organizations, archives, societies, and individuals will coordinate efforts to provide quick access to these digital images and immediately start indexing these records to make them searchable online for free and open access. Through this joint initiative, the index and images will always be available for free on FamilySearch.org.
How quickly these records get published depends on how many volunteers help. FamilySearch currently has a lot of great indexers like you, but we're going to need tens of thousands more in order to get these records published sooner without sacrificing quality. If we all work together and get our friends and neighbors involved in indexing, we can all be searching these records in no time."
excerpted from: 1940 U.S. Census Is Coming! Don't Flip Your Wig. FamilySearch Is Cooking with Gas. December 16, 2011: by GaleK