If the "terrorists" are following this whole story, wouldn't now be a prime time for another attack? This could have the effect of validating the NSA's activities in many Americans' eyes ("see, the NSA is unable to its job without invading our privacy") and we would see a whole new round of new laws capitalizing on Americans' fears of terrorists (which means their terrorism succeeded).
Assumption #2: That successful attacks in this scenario would lead (reasonable or otherwise) people to demand less surveillance.
Assumption #3: Terrorists want to the NSA programs ended, which would not make sense if #1 is true.
So I'm not sure why this would be a good strategy for anyone.