My 2008 BMW has this feature. It is nice to have, but the headlamps are complex, thus expensive. They turn mechanically (electrically powered) at +-15 degrees, following the road. Someone noted above that they only turn to one side (left). That is not true. When stopped, they only turn to the right, in my case, as to not blind oncoming traffic in case you are stopped on the side of the road. The Lexus above might turn only to the left when stopped as it's a Japanese car (or the adaptive light system might be defective). When driving, they turn in both directions, lighting the place where the car will go (based on speed, steering angle and possible other sensors).
If Tesla decides to implement this, it will only be possible on newly manufactured cars and will double the price of the Xenon headlamps.
Sorry, but the Model S does not have adaptive headlights. The tech package does include "Xenon headlamps".
I have adaptive headlights on my Lexus, and it is a mildly nice to have. I only occasionally drive on completely dark curvy roads in the country, where it has more value. That said, I wouldn't pay anything extra for it myself. I had one headlight damaged and it cost over $1000 for the replacement. I suspect that's in part due to the complexity of the headlight assembly.