"Released" is in quotes because of course searching for grandma is not what I'm interested in, and that's all the capability I can find right now. The National Archives website for the census is here, though. I don't see any note about it in my usual source for census microdata, the IPUMS. If anyone knows where to get 1940 microdata or if this is being released, could you let me know?
There's lots of great information on New Deal program participation that looks particularly interesting.