I was flipping through the new flyer that came in the mail today from a popular video game store chain in Holland and it showed D3 coming out on April 19th, which happens to be on a tuesday.
Also I went to the web site and it also gave this informaion as well:
http://www.bartsmit.com/pc-dvd-diablo-3
Of course it could be made up date, placeholder date, just a random date to signify Q2. But usually Bart Smit is right on the money when it comes to product releases.
Just a heads up, dont look too much into it.