If you think that's a possible reality you're living in a paranoid lala land - which isn't surprising given all the apocalyptic narratives we get from the media (gov't turning evil, zombies/robots taking over, evil agencies controlling the world).
The reality is that no wealthy democratic government in the past 50 years (some of which are less obsessed with protecting liberties) has slid back into tyranny. There are statistics that indicate that past a certain GDP threshold tyrannical governments become unsustainable.
This kind of thing is simply never going to happen.