1. Into Darkness earned $70 million it's opening weekend. Star Trek earned $75 million.
2. Industry analysts and the studio expected $90-$100 million, so it's far short of expectations.
3. Studios DO NOT, I repeat, DO NOT expect sequels to earn less than their predecessors, especially when the budget of the sequel is $40 million more than the original. Look no further than Spiderman 2, The Dark Knight, The Matrix Reloaded, Pirates of the Caribbean: Dead Man's Chest, etc. Iron Man 2 was slightly below Iron Man ($6 million less) but Iron Man 3 has already exceeded both films.
4. Into Darkness will likely earn its $190 million dollar budget back domestically (minus marketing, of course) but it won't be a major earner and will certainly have a disappointing take. Generally speaking, a film begins to decline in its second week of release by 50%. Given that next weekend is a 3 day holiday, it's likely that Star Trek will only see a modest loss of maybe 30%-40%, so the total would be around $135 million or so in week two (and I'm being optimistic).
By week three, the domestic gross would likely be around $20 million and by week four, all bets are off because The Man of Steel is released and it will get crushed. $10 million in week four would be huge.
So for the sake of guessing, that puts the film at the following:
Week 1: $85 million
Week 2: $50 million ($135)
Week 3: $20 million ($155)
Week 4: $10 million ($165).
By the end of an 8 week run, it should probably reach $190 million but that isn't exactly a given, especially when considering the tepid response the film received this weekend and the other choices available in Iron Man 3, Man of Steel, in a addition to Monsters University and World War Z the weekend of June 18th.
If it hasn't hit its budget by the end of June, it's dead in the water.