Yeah, that's what's going to happen. The problem is that we get a lot of good leads from prisoners that lead us to more terrorists. It's not like we're exactly tripping over good intelligence these days, and can afford to just toss out one of our best sources. A loss of intelligence leads directly to a decrease in our ability to stop terrorism. Period.
If we have to provide terrorists a full legal defense, complete with a lawyer advising them not to incriminate themselves, then forget about it. News of this legislation is already making the rounds among the insurgency and the terrorists, and when it passes it will be celebrated.