Judging by a NYU's professor's regression model on how opening weekend box office numbers predict total movie grosses, and adjusting downward due to expected higher-than-normal opening weekend geek fandom, we'd expect this film to eventually gross about, or just above, $130 million domestically when all is said and done (Paramount holds overseas rights). Funny enough, that happens to be the same figure as the reported budget of the film.
I don't think WATCHMEN will "damage" the careers of any of the cast members. All of them have run themselves ragged to promote the movie, and all of them are capable actors. Even Malin Ackerman, the cast member singled out as the "weak link," just as Laurie is often considered the "weak link" of the graphic novel.
None of the cast members are straight-up movie stars, but this might give each actor and actress chances at bigger roles. Zach Snyder has been declared a "visionary director," so he's set.
Here are some links.