The Presidential Records Act mandates the preservation of all presidential records. At least in theory this means that the only Presidential communications immune from further scrutiny are phone calls (which are not recorded) and verbal in-person conversations. Presumably this might create a bit of a bias against written communication, as there's plenty of discussions that the White House might not want to be exposed in the future.
Has there been any academic research on the effects of this Act on communications within the White House since 1971?