It will be made illegal. In many ways it already is. You must submit the key to encrypted material if proper law enforcement asks. Your lines are allowed to be tapped. Your locks are allowed to be broken.
The problem is not the agency, but the paranoid and ruthless people who abuse it. There are many people in law enforcement/intelligence communities who are honest law abiding citizens! There are a few who are not. The question becomes how do we watch the watchers? How do we catch the abusers? I am not sure this will ever be an easy thing to do. Knowledge is the most powerful tool one can have, and for those with an illegal or perverse agenda, the gathering of information provides opportunities to gain leverage over others, advantages in business and political dirt to get what they want. So, they will always try to use the system.
So long as the people who take power (not the elected officials, but the string pullers), have that power, and we the people allow them to, this is how it will be. There is no way at the moment to record anything and expect absolute security. I am not sure your own mind will be safe for much longer. It has always been this way. There is always someone, or a few people conspiring to control as much as possible around them through whatever means, legal, moral, ethical or not to do what they want. Some do it in the name of a god, some in the name of patriotism, some just because it is what they want.
What really needs to be figured out is how to stop these people from doing what they do. I do not think it is possible, as the people stopping them will most likely be those people.