The Times has an analysis of the new legislation on terrorism which includes these thoughts:
The last paragraph is what I'm inclined to think.
How the measure will look decades hence may depend not just on how it is used but on how the terrorist threat evolves. If a major terrorist plot in the United States is uncovered — and surely if one succeeds — it may vindicate the Congressional decision to give the government more leeway to seize and question those who might know about the next attack.
If the attacks of 2001 recede as a devastating but unique tragedy, the decision to create a new legal framework may seem like overkill. “If there is never another terrorist attack and we never obtain actionable intelligence, this will look like a huge overreaction,” said Gary J. Bass, a professor of politics and international affairs at Princeton.