The final outing for Summit Entertainment's blockbuster Twilight franchise could have the sharpest bite of all. Most box-office observers believe The Twilight Saga: Breaking Dawn -- Part 2 will score a franchise-best opening at the domestic box office with a $145 million to $150 million debut, beating record holder 2009's New Moon ($142.8 million). Breaking Dawn 2 begins rolling out in North America at 10 p.m. Thursday; by Friday morning, it will be playing in 4,070 theaters. Summit is predicting a more conservative domestic opening and says Breaking Dawn 2 is tracking more in line with last year's Breaking Dawn -- Part 1 , which grossed $138.1 million on the same weekend a year ago. Breaking Dawn 2 has several factors in its favor, however. It's the final film in the series, which should generate additional heat, and the North American box office has been generating strong results for popular event titles. Online ticketing service Fandango reports that th