As someone who's a big enough Mass Effect nerd to have, say, actually read the novels that people were citing as "evidence" that supported the theory, I never thought it made any damn sense to begin with. Furthermore, I never understood why anyone thought that, as horrible as the original ending was, "it was all a dream" was somehow a better solution.
Regardless, it's pretty obvious that it's never been even remotely close to Bioware's version of events so I'd say yeah, it's deader than A-line flares with pockets in the knees.