I wouldn't have thought they are stopping him from getting killed off, the whole point of the movie from what I can tell is that all the Joes have been killed apart from the main cast. If they wanted him to survive they would have to reshoot a lot and I don't know why they would bother, especially as Tatum is just as likely to drive people away than bring them in. I think more likely they will be expanding his role before the attack on the Joes, which is probably more of an editing thing rather than reshoots. Besides, it doesn't take 9 months to change it to not kill off Duke, all you need to do is redub it to say that the snake speared through his chest just put him into a coma and have someone say "Duke woke up!" at the end of the movie and everyone cheer.
