It showed up in an article about a month before March 11th earthquake. I believe D800 was ready for launch at that time.
source http://www.flixya.com/blog/2339880/Rumor-Nikon-D800-24-megapixel-sensor-Coming-Soon
A screenshot of a related article in Amateur Photographer:
source: (http://www.amateurphotographer.co.uk/news/nikon_d800_dslr_due_before_february_2011_update_news_302529.html):
And a link to the article about that D800 book:
http://www.amazon.fr/Obtenez-maximum-du-Nikon-D800/dp/2100541021
I hope by clearly mentioning the source of my screenshot the site owner won't delete my screenshot anymore.
