The model S was introduced in 2012 and has mostly remained the same. In 2016 The nose was updated, losing the front grill. A refreash was a long time coming.
I have a 2013 Model S, which I love. It has been my daily driver.
So probably the biggest change is going to be the center screen. The orientation has changed to horizontal instead of portrait much like that of the Model 3 and Model Y. Even though I have come to love the vertical screen in my Model S, I know it is not optimal for viewing video and playing games. Tesla says the new center screen is basically a gaming computer with 10 teraflops of processing power, nearly as much gaming power of a Playstation 5. And thankfully the S keeps digital gauge cluster in front of the driver, as well.