yes but as long as the laser beam can carry absurd amounts of data, that linear coefficient is just fine. Nobody needs to sync trillions of cat videos (which is the source of exponential growth) between Mars and Earth.
No, the nature of technology building upon itself is the source of exponential growth. As long as storage and processor technology continues to improve - and it will - we will find uses for that space, and network technology will need to keep up.
