if it was going to continue in the new season, the end would be perfect but now that the show has ended with that episode, i think it is not that great. we had an open end that makes us curious about what happened next. nothing went right according to the first flashforward so maybe this was a way to say people that nothing can be guessed. even though the end was not clear, the show was the best of it's season on its own category.
i hope that the producers won't give up and they will keep making shows like this.