Stephenie Meyer alisema that it might not be possible to make Breaking Dawn. This is purely because of Renesmee. The baby has to be alert from the dakika she's born and it's not possible to find a baby that alert. The baby also has to grow at an alarming rate and look the same the whole way through, but you'd need a bunch of actors to do it. The only possible way to do it is through CGI and so far no CGI people have ever looked completely real, and that's Stephenie's concern with making the film. Hope this helped!