I doubt they'll add new music for existing situations. So probably no new supercruise, arriving at destination, or combat music is going to get added into the rotation. But they might create new music for new situations, points of interest, etc. Seems likely that there could be some new "fighting thargoids" music once the scouts start showing up.
There is only like 3 supercruise songs? That is inadequate. Imagine playing this game for 80 hours and hear the same supercruise songs 100 times. That's not good. It needs more variety.