I've never heard of any ever going to see a film "just to see the trailer". The Hostel/Hostel 2 argument is even more hilarious. See No Evil? Are you serious?
But anyway, back to the subject. Sweeney Todd won't be #2 anymore than I Am Legend will be #1 again. National Treasure should knock it to #2 and Dewy Cox will give them a run for their money on 2,500 screens. Sweeney Todd is only on 1,000 screens and definitely doesn't appeal to a wide audience.