I was watching this thread while working on the new content to add, but nobody outside the ASIM's and myself knew that it was coming. New galaxy content doesn't get shared or announced to anyone until it has been revealed, ASIM's don't even have access to view planet locations.
What Jevon said is still true, I cannot add hidden sectors in the same sense as hidden systems. Once given coordinates they will show on the map like every other sector.
The primary reason for adding a new sector is because all of our existing content comes from what is now Legends, where as any new stuff added in books or movies comes from Canon. Most of the time the locations will match, but in some instances the sector information clashes or puts things in different parts of the galaxy, or in sectors that don't exist. I am constantly working to add new content, that will benefit players, and fit within the greater galaxy that exists.
In this case a new sector was the best route. That won't usually be the case, but I won't write out adding others down the road. Either way, if a sector is added, it will be visible so don't bother trying to search for planets outside of visible sector boundaries.