Update: the photographer posted this comment on his Facebook page:
"This has gone so far. I'm just joking among friends. I didn't write anything about it, just posted the photo, no description. But you have to wait for the news at the end of this month. There's a new model, not sure if it's this name (D400). Someone already tested it while I just had a look. Sorry for the panic. Let's talk again at the end of July"
This screenshot was published on the facebook account of Waran Suwanno (pictures; websites: pixpros, pixproshouse) - a well respected photographer from Thailand. The rumor is that he did test Nikon equipment in the past. The screenshot is a Capture NX2 window showing Nikon D400 listed in the camera info window.