Nah, WB is not profiting $350M on a film that grossed $700M, especially when most of that gross is outside of the US. For them to profit like that, that would mean every dollar this movie makes goes to the studio, and that's not the case at all. The film has a $200M budget, and when you factor in marketing, and the actual cut WB gets, they might make a small profit by the end of it.
FB2 will be profitable. That is not the issue. The issue is whether FB3 can be profitable if the franchise continues to drop off.
If the next one is 125M domestic and maybe 575M worldwide, what happens? WB takes a bath is what would happen if they don't seriously cut the budget down.