Are NFL defenders now required to read ball carrier's minds when they are close to being out of bounds?

I'm pretty sure I saw a call in a game last week where a defender got an "unnecessary roughness" penalty for putting a lick on a runner who was still clearly in bounds but looked to be heading out. So what happens to a defender who lays off of a guy "clearly going out of bounds" who loses his job because the ball carrier cuts it back inside and runs for a touchdown?