Box office forecasters appear to have little doubt that 20th Century Fox's Avatar will hold on to the top position at both the domestic and international box offices this weekend, probably racking up another $25-30 million domestically. That would bring its domestic total to more than $550 million -- within striking distance of the record $601 million earned by James Cameron's previous film, Titanic. Three new films are opening wide, but none is expected even to come close to Avatar 's figures. Fox will be competing against itself with the family comedy Tooth Fairy, starring wrestler-turned actor Dwayne Johnson, while Sony/Screen Gems offers the sci-fi action flick Legion, starring Lucas Black and Paul Bettany. (The latter was not screened for critics.) Neither is expected to gross more than $15-18 million. A third film, Extraordinary Measures, marking the debut of CBS Films in the theatrical marketplace, is not expected to do more than $6-8 million, despite the marquee attraction of its stars, Harrison Ford and Brendan Fraser. All three films drew mostly negative reviews.