Could "Eclipse" actually make less than "New Moon"? 

it could, we won't know tell it comes out, but if you look at other franchise films the third film always seems to make a little less a the box-office, examples: sherk the third, spiderman 3, harry potter and the prisoner of azkaban, pirates of the caribbean 3, all still made a lot of money at the box-office but not as much as the first 2 films in their franchises