Here is the source: http://www.gamasutra...php?story=16626
Amd this is their source (lol): http://forums.worldo...&sid=1&pageNo=1
IT IS OFFICIALLY CONFIRMED.
Edit: Well... calling it Diablo 3 is speculation because of the focus on the term 'unannounced title.'
For conversation's sake, what is a "Title" anyway?