I refer the right honourable gentleman to the answer I gave a moment ago.
Fair enough. However, my point is that, in the movie, they gave a hope of saving those people's lives. The television show would presumably give the same hope. In order to do that, they have to leave open the possibility of being able to change time. The movie seemed to leave open this possibility as well. So far, the concept is exactly the same. The only difference is we've seen the movie and know that they were just teasing us when they seemed to leave it open.
This discussion started with the idea that watching a television series where we knew most of the people we meet are going to die would be a downer. I tend to agree, but I don't think being faithful to the source material requires this.