Nothing will change.
That means, when Brennan vowed to protect and defend the Constitution, he was swearing on one that did not include the First, Fourth, Fifth, or Sixth Amendments — or any of the other Amendments now included in our Constitution. The Bill of Rights did not become part of our Constitution until 1791, 4 years after the Constitution that Brennan took his oath on.
I really don’t mean to be an asshole about this. But these vows always carry a great deal of symbolism. And whether he meant to invoke this symbolism or not, the moment at which Brennan took over the CIA happened to exclude (in symbolic form, though presumably not legally) the key limits on governmental power that protect American citzens.