It doesn't become unconstitutional when a court says so. From its inception either it is, or it isn't. The issue simply isn't decided until the court says so.
Right. The NSA can make a good faith argument that they designed the program to stay within the bounds of Constitutionality. Their opinion can't override that of the Supreme Court, but until the Supreme Court rules they are entitled to try and interpret the law and act accordingly.
From a practical point of view there's no difference, we can split hairs if you want.