This is a more complex question than I initially thought, and most of that stems from some weird wording in the NFL rules. The provision that allows the QB to throw the ball away once he's outside the tackle position refers specifically to that - "the tackle position." (Rule 8, Section 2, Article 1, Item 1.) However, the tackle position is never fully defined. What is defined is the tackle box (Rule 3, Section 35) and the pocket area (Rule 3, Section 25). The pocket area refers to the "normal tackle position," which is a little subjective, but I think we can agree that Vereen is not in the normal tackle position in the above picture, but rather that the lineman second from the right of the center is in the normal tackle position.
The rules make reference to the tackle box when talking about unsportsmanlike conduct penalties (horse collar tackle, illegal chop blocks, illegal hits on defenseless players) but not in the rules on intentional grounding. The pocket area is referred to in the intentional grounding rule, even if not specifically in the section that concerns your situation. So I would say that we use the definition of the pocket, and not that of the tackle box, to determine whether or not intentional grounding has been committed; this takes us back to the "normal tackle position." (For what it's worth, the tackle box extends from "tackle to tackle" and I think you'd be hard pressed to define Vereen as the right tackle here, considering there is a traditional right guard and tackle on the line as well.)
To further my case, it seems most of the talk about this play has referred to the Pats having 4 offensive lineman, and not counting Vereen as one of them. (A couple different tweets and people refer to that in this SB Nation article on it.)
Ultimately, there definitely is some ambiguity here, and I think there's some leeway for the referee to decide for himself, but looking at what I see here, I'd say that if Brady makes it outside of the traditional tackle box but is still inside of Vereen's position, he wouldn't get called for grounding.
All the rules I referenced in here come from this edition of the rules on the NFL website. (Warning: that is a rather large PDF).