Assuming the production budget is the rumoured $150 million, it'll have to rake in at least $300-350 million worldwide to make a profit and justify Paramount's investment in it. If they're counting on DVD sales and merchandising to help generate revenue, the box office expectations might be downplayed slightly.
A friend and I have been debating how much money we think Star Trek is likely to make. He thinks it's going to top out at $150 million at the US Box Office and around $230 million worldwide, using the aforementioned DVD sales and merchandising to make up the shortfall. I'm more optimistic, hoping that it can break the $200 million barrier in the US and go on to rake in just north of $300 million worldwide. It's highly unlikely to post Transformers or Dark Knight style numbers, but it's also unlikely to be as big a box office disappointment as Insurrection and Nemesis were.