Based on what I saw in a limited peek at practice this week, my feeling is that it wouldn't be a surprise if Gronkowski remains sidelined. He is still limited. For example, when players went through a gauntlet in which teammates whacked them with pads in an attempt to jar the ball free, Gronkowski only played the role of the "whacker" and never ran through.
Former Pats assistant coach Michael Lombardi was quoted in the story as saying Bill Belichick's philosophy is if a player is injured a team is better off playing a backup. That may especially be true in Week 2 after coming off a Week 1 win without Tom Brady. It's only one opinion, but owners should prepare a backup plan.