http://www.pcgamer.com/2011/08/01/diablo-3-cannot-be-played-offline/
I check with him to be absolutely sure: there’s no way to play without being online? “There’s no offline play, you have to be connected to the internet.”
There is nothing here that is vague, evasive, or open to interpretation. I'm not sure how you get "we know nothing about this". Your only argument is, "they could still change their mind before release."
In which case I will reconsider.
--
From his looks Magus is Macho Man Randy Savage as an anime zombie. The black wind howls, and one of you will snap into a Slim Jim ooh yeeeah! -sonicblastpunch