It cost 190m and they marketed it pretty heavily for what could be a marginal gain or even slightly less than. We'll have to wait and see about overseas too, if it doesn't improve significantly overseas then it'll be a stretch to say we'll get a sequel. If it gets to 2009's gross and the overseas reaches 250m then it'll get a sequel.
What it does have going for it is that it might get something being released a year after Star Wars, the 50th Anniversary, and the blu ray sales are always very strong for Trek. Not to mention, once again, it's scored well with audiences and critics alike so Paramount could decide to look at their marketing again.